Science is an enterprise concerned with gaining information about causality, or the relationship between cause and effect. A simple example of a cause is the movement of a paddle as it strikes a ping-pong ball; the effect is the movement of the ball through the air. In psychology and other sciences, the word "cause" is often replaced by the term "independent variable". This term implies that the experimenter is often "free" to vary the independent variable as he or she desires (for example, the experimenter can control the speed of the paddle as it strikes the ball). The term "dependent variable" replaces the word "effect", and this term is used because the effect depends on some characteristic of the independent variable (the flight of the ball depends on the speed of the paddle). The conventions of science demand that both the independent and dependent variables be observable events, as is the case in the ping-pong example. In the case of biorhythm theory, the independent variable is the number of days that have elapsed between a person’’s date of birth and some test day. The dependent variable is the person’’s level of performance on some specified task on the test day. Notice that although the experimenter is not free to choose a birthday for a given individual, persons with different dates of birth can be tested on the same day, or a single subject can be tested on several different days. 　　In order to predict the relationship between independent and dependent variables, many scientific theories make use of what are called intervening variables. Intervening variables are purely theoretical concepts that cannot be observed directly. To predict the flight of a ping-pong ball, Newtonian physics relies on a number of intervening variables, including force, mass, air resistance, and gravity. You can probably anticipate that the intervening variables of biorhythm theory are the three bodily cycles with their specified time periods. It should be emphasized that not all psychological theories include intervening variables, and some psychologists object to their use precisely because they are not directly observable. 　　The final major component of a scientific theory is its syntax, or the rules and definitions that state how the independent and dependent variables are to be measured, and that specify the relationships among independent variables, intervening variables, and dependent variables. It is the syntax of biorhythm theory that describes how to use a person’’s birthday to calculate the current status of the three cycles. The syntax also relates the cycles to the dependent variable, performance, by stating that positive cycles should cause high levels of performance whereas low or critical cycles should cause low performance levels. To summarize, the components of a scientific theory can be divided into four major categories: independent variables, dependent variables, intervening variables, and syntax. The word "syntax" used in the last paragraph refers to the

A:rules used for ordering and connecting words in a sentence. B:principles defining the connections among different variables. C:definitions describing the impact of biorhythm on one’’s behavior. D:criteria measuring a person’’s performance levels with biorhythm.

A very rapid increase in the number of ships sailing between American and European ports began almost immediately after the end of the war of 1812 in order to meet the new need for the regular rapid transportation of mail, light cargo, and passengers. It was the increase in emigration to America that for the first time made the carrying of passengers across the Atlantic more profitable than the transportation of heavy cargo. A new type of sailing vessel, the packet, appeared to meet this new demand, and the extent of the demand very soon resulted in strong competition among several packet lines. The earliest to these was the Black Ball Line established in New York in 1816, only a year after the end of the war. The scheduled service of this famous line started with four of the new fast packets, each of 400 to 500 tons: the Pacific, the Amity, the James Cooper, and the William Thompson. During the first twenty years of service, the average time from New York to Liverpool was 23 days and the average trip back to New York took 40 days.By the middle of the century, packets had increased in size to between 900 and 1,000 tons, and their speed had increased. The Red Jacket once sailed from New York to Liverpool in 13 days, 11.5 hours. The Mary Whiteridge took 4.5 hours off this record on a run from Baltimore to Liverpool. Such speeds were far greater than the average of from 19 to 21 days to Liverpool and from 30 to 35 homeward to New York, but the packet had still set a new standard for transoceanic travel. No wonder that steamships, the first of which tried to compete with the packets in 1838, only began to replace them in the 1850’s.

A:11.5 hours B:7.5 hours C:7 hours D:4.5 hours

The elapsed time of the fastest transatlantic crossing mentioned by the author was 13 days and ______.

A:11.5 hours B:7.5 hours C:7 hours D:4.5 hours

Edwin Hubble Edwin Hubble changed our ideas about the universe and how it developed. The work of few other scientists changed our understanding of 【51】 suddenly. He made his most important discoveries in the 1920s. Today, other scientists continue the work he began back then. Edwin Powell Hubble was born in 1889 in Marshfield, Missouri. He 【52】 his early years in the state of Kentucky. Then he moved with his family to Chicago, Illinois. He attended the University of Chicago, taking mathematics and astronomy 【53】 his specialty. As a student, Hubble was also a member of the University’’s basketball team and an excellent boxer. Several people urged him 【54】 for the world heavy weight boxing championship after college. Instead he decided to continue his 【55】 . In his first observations from Mount Wilson, California, Hubble used a telescope with one-hundred fifty-two and began 【56】 more and more distant objects. His first great discovery was made 【57】 he recognized a Cepheid variable star. Cepheid variable stars are stars whose brightness changes at regular periods. Hubble then began to observe more details about galaxies. He studied their shapes and brightness. By 1925, he had made enough observations to say that the universe is organized into many shapes and sizes. As stars differ from one another, he said, 【58】 galaxies. According to his observations, the galaxies have a center, and arms of matter that seem to the center like a pinwheel. Other are shaped 【59】 baseballs or eggs. A few have no special 【60】 Hubble proposed a system to describe galaxies by their shape. His system is still used today. He also showed that 【61】 are similar in the kinds of bright objects they contain. All galaxies, 【62】 , are related to each other much as members of a family are related to each other. In the late 1920s, Hubble studied the movement of galaxies through space. His investigation led to the most important 【63】 discovery of the 20th century—the expanding universe. Hubbies discovery 【64】 a major change in our ideas of the universe. The universe had not been quiet and unchanging since the beginning of time, as many people had thought. It was expanding. The expanding often is 【65】 the Big Bang.

A:took B:past C:spent D:elapsed

Edwin Hubble Edwin Hubble changed our ideas about the universe and how it developed. The work of few other scientists changed our understanding of 【51】 suddenly. He made his most important discoveries in the 1920s. Today, other scientists continue the work he began back then. Edwin Powell Hubble was born in 1889 in Marshfield, Missouri. He 【52】 his early years in the state of Kentucky. Then he moved with his family to Chicago, Illinois. He attended the University of Chicago, taking mathematics and astronomy 【53】 his specialty. As a student, Hubble was also a member of the University’’s basketball team and an excellent boxer. Several people urged him 【54】 for the world heavy weight boxing championship after college. Instead he decided to continue his 【55】 . In his first observations from Mount Wilson, California, Hubble used a telescope with one-hundred fifty-two and began 【56】 more and more distant objects. His first great discovery was made 【57】 he recognized a Cepheid variable star. Cepheid variable stars are stars whose brightness changes at regular periods. Hubble then began to observe more details about galaxies. He studied their shapes and brightness. By 1925, he had made enough observations to say that the universe is organized into many shapes and sizes. As stars differ from one another, he said, 【58】 galaxies. According to his observations, the galaxies have a center, and arms of matter that seem to the center like a pinwheel. Other are shaped 【59】 baseballs or eggs. A few have no special 【60】 Hubble proposed a system to describe galaxies by their shape. His system is still used today. He also showed that 【61】 are similar in the kinds of bright objects they contain. All galaxies, 【62】 , are related to each other much as members of a family are related to each other. In the late 1920s, Hubble studied the movement of galaxies through space. His investigation led to the most important 【63】 discovery of the 20th century—the expanding universe. Hubbies discovery 【64】 a major change in our ideas of the universe. The universe had not been quiet and unchanging since the beginning of time, as many people had thought. It was expanding. The expanding often is 【65】 the Big Bang.

A:took B:past C:spent D:elapsed

Edwin Hubble Edwin Hubble changed our ideas about the universe and how it developed. The work of few other scientists changed our understanding of 【51】 suddenly. He made his most important discoveries in the 1920s. Today, other scientists continue the work he began back then. Edwin Powell Hubble was born in 1889 in Marshfield, Missouri. He 【52】 his early years in the state of Kentucky. Then he moved with his family to Chicago, Illinois. He attended the University of Chicago, taking mathematics and astronomy 【53】 his specialty. As a student, Hubble was also a member of the University’’s basketball team and an excellent boxer. Several people urged him 【54】 for the world heavy weight boxing championship after college. Instead he decided to continue his 【55】 . In his first observations from Mount Wilson, California, Hubble used a telescope with one-hundred fifty-two and began 【56】 more and more distant objects. His first great discovery was made 【57】 he recognized a Cepheid variable star. Cepheid variable stars are stars whose brightness changes at regular periods. Hubble then began to observe more details about galaxies. He studied their shapes and brightness. By 1925, he had made enough observations to say that the universe is organized into many shapes and sizes. As stars differ from one another, he said, 【58】 galaxies. According to his observations, the galaxies have a center, and arms of matter that seem to the center like a pinwheel. Other are shaped 【59】 baseballs or eggs. A few have no special 【60】 Hubble proposed a system to describe galaxies by their shape. His system is still used today. He also showed that 【61】 are similar in the kinds of bright objects they contain. All galaxies, 【62】 , are related to each other much as members of a family are related to each other. In the late 1920s, Hubble studied the movement of galaxies through space. His investigation led to the most important 【63】 discovery of the 20th century—the expanding universe. Hubbies discovery 【64】 a major change in our ideas of the universe. The universe had not been quiet and unchanging since the beginning of time, as many people had thought. It was expanding. The expanding often is 【65】 the Big Bang.

A:took B:past C:spent D:elapsed

Edwin Hubble Edwin Hubble changed our ideas about the universe and how it developed. The work of few other scientists changed our understanding of 【51】 suddenly. He made his most important discoveries in the 1920s. Today, other scientists continue the work he began back then. Edwin Powell Hubble was born in 1889 in Marshfield, Missouri. He 【52】 his early years in the state of Kentucky. Then he moved with his family to Chicago, Illinois. He attended the University of Chicago, taking mathematics and astronomy 【53】 his specialty. As a student, Hubble was also a member of the University’’s basketball team and an excellent boxer. Several people urged him 【54】 for the world heavy weight boxing championship after college. Instead he decided to continue his 【55】 . In his first observations from Mount Wilson, California, Hubble used a telescope with one-hundred fifty-two and began 【56】 more and more distant objects. His first great discovery was made 【57】 he recognized a Cepheid variable star. Cepheid variable stars are stars whose brightness changes at regular periods. Hubble then began to observe more details about galaxies. He studied their shapes and brightness. By 1925, he had made enough observations to say that the universe is organized into many shapes and sizes. As stars differ from one another, he said, 【58】 galaxies. According to his observations, the galaxies have a center, and arms of matter that seem to the center like a pinwheel. Other are shaped 【59】 baseballs or eggs. A few have no special 【60】 Hubble proposed a system to describe galaxies by their shape. His system is still used today. He also showed that 【61】 are similar in the kinds of bright objects they contain. All galaxies, 【62】 , are related to each other much as members of a family are related to each other. In the late 1920s, Hubble studied the movement of galaxies through space. His investigation led to the most important 【63】 discovery of the 20th century—the expanding universe. Hubbies discovery 【64】 a major change in our ideas of the universe. The universe had not been quiet and unchanging since the beginning of time, as many people had thought. It was expanding. The expanding often is 【65】 the Big Bang.

A:took B:past C:spent D:elapsed