Researchers have found that REM (rapid eye movement)sleep is important to human beings. This type of sleep generally occurs four or five times during one night of sleep lasting five minutes to forty minutes for each occurrence. The deeper a person’s sleep becomes, the longer the periods of rapid eye movement.
There are physical changes in the body to show that a person has changed from NREM (non-rapid eye movement)to REM sleep. Breathing becomes faster, the heart rate increases, and, as the name implies, the eyes begin to move quickly.
Accompanying these physical changes in the body there is a very important characteristic of REM sleep. It is during REM sleep that a person dreams.
Which of the following shows that a person is NOT dreaming in his sleep
A:His eyes begin to move. B:His breathing becomes faster. C:His heart rate increases. D:His eyes stop movin
(If) traffic problems are not solved soon, (driving) (in) cities (becomes) impossible.
A:If B:driving C:in D:becomes
阅读下面的短文，文中有15处空白，每处空白给出4个选项，请根据短文的内容从4个选项中选择1个最佳答案。
? ? Energy equals mass times the speed of
light squared. This is the famous equation of Albert Einstein. It{{U}} ?(51)
?{{/U}}to the category of the theory of relativity, and it equates energy
with mass.
? ?All things are made up of atoms. When{{U}} ?(52)
?{{/U}}of an atom travels at almost the speed of light{{U}} ?(53)
?{{/U}}we put more energy into it to increase the speed, it begins to in
crease in mass. The energy that makes it travel fast cannot make it travel{{U}}
?(54) ?{{/U}}the speed of light—nothing{{U}} ?(55) ?{{/U}}light
can travel that fast- so the energy goes into the thing{{U}} ?(56)
?{{/U}}and increases its mass. Energy{{U}} ?(57) ?{{/U}}into
mass.
? ?Why is the theory called the theory of relativity? A thing
that is relative depends upon{{U}} ?(58) ?{{/U}}else to identify it or to
define it. In relativity theory we identify or define mass, time, and length{{U}}
?(59) ?{{/U}}to the speed of light.
? ?When something is at
rest, it looks{{U}} ?(60) ?{{/U}}in length. However, when it travels at
almost the speed of light, it becomes{{U}} ?(61) ?{{/U}}. Time also
changes. However, the change in time is{{U}} ?(62) ?{{/U}}to the change in
length. The length of a thing becomes short{{U}} ?(63) ?{{/U}}time becomes
long.
? ?If you want to{{U}} ?(64) ?{{/U}}young, relative to
a friend, take a trip in a spaceship that travels at{{U}} ?(65) ?{{/U}}the
speed of light. And, although time and heartbeat seem ordinary to you in the
spaceship, when you return, look at your friend; Relative to you, he or she is
old. |
A:changes B:becomes C:shifts D:turns
Nevertheless, hand - washing is still your best defense against getting sick generally this fall - colds and other respiratory diseases are no fun, even if they don’t sound as scary as swine flu. For that and other flu viruses, don’t seek solutions at the sink: your best chance of avoiding H1N1 this fall is to get the vaccine once it becomes available.
"At the sink" in the paragraph refers to the effort to avoid being infected by flu viruses
A:before the disease becomes too serious. B:by hand - washing. C:by getting the vaccine. D:before you are surrounded by carriers.
Nevertheless, hand - washing is still your best defense against getting sick generally this fall - colds and other respiratory diseases are no fun, even if they don’t sound as scary as swine flu. For that and other flu viruses, don’t seek solutions at the sink: your best chance of avoiding H1N1 this fall is to get the vaccine once it becomes available.
"At the sink" in the paragraph refers to the effort to avoid being infected by flu viruses
A:before the disease becomes too serious. B:by hand - washing. C:by getting the vaccine. D:before you are surrounded by carriers.
When lava cools, it becomes
A:liquid. B:water. C:smoke. D:hard.
When lava cools, it becomes
A:liquid. B:water. C:smoke. D:hard.
单选集填空
