Directions: There are 5 passages in this part. Each passage is
followed by some questions or unfinished statements. For each of them there are
4 choices marked A, B, C and D. You should decide on the best choice and mark
the corresponding letter on your Answer Sheet with a single line through the
center.
Passage 1
Population tends to grow at an
exponential(指数的)rate. This means that they progressively double. As an example
of this type of growth rate, take one penny and double every day for one month.
After the first week, you would have only 64 cents, but after the fourth week
you would have over a million dollars.
This helps explain why
the population has come on "all of a sudden". It took from the beginning of
human life to the year 1830 for the population of the earth to reach one
billion. That repents(缓慢进行)a time span of at least two million years. Then it
took from 1830 to 1930 for world population to reach 2 billion. The next billion
was added by 1960, only thirty years, and in 1975 world population reached 4
billion, which is another billion people in only fifteen years.
World population is increasing at a rate of 9000 per hour, 220000 per day,
and 80 million per year. This is not only due to higher birth rate, but to lower
death rate as well. The number of births has not declined at the same rate as
the number of deaths.
Some countries, such as Columbia,
Thailand, Morocco, Costa Rica, and the Philippines, are doubling their
population about every twenty-one years, with a growth rate of 3.3% a year or
more. The United States is doubling its population about very eighty-seven
years, with a rate of 0.8% per year. Every time a population doubles, the
country involved needs twice as much of everything, including hospitals,
schools, resources, food and medicines to care for its people. It is easy to
see that this is very difficult to achieve for the more rapidly growing
countries. |
According to the passage, what helps to explain why the population problem has come on "all of a sudden" ______.
A:The penny that doubles itself every day for one month B:The time span of at least two million years in human history C:An illustration of the exponent growth rate given by the author D:The large amount of money you would luckily make after the fourth week
A floating constant consists of an integer part，a decimal point，a fraction part，an e or E，and an optionally signed integer ．
A:exponent B:order C:superfluous D:superior
A floating constant consists of integer part,a decimal point,a fraction part,an e or E,and an optionally signed integer（）
A:exponent B:order C:superfluous D:superior
A floating constant consists of an integer part, a decimal point, a fraction part, an e or E, and an optionally signed integer（）
A:exponent B:order C:superfluous D:superior
A floating constant consists of an integer part, a decimal point, a fraction part, an e or E, and an optionally signed integer（）
A:exponent B:order C:superfluous D:superior
单项选择题
