[单项选择]Scientists have advanced many theories about why human beings cry tears , none of （） has been proved.
A. whom
B. which
C. what
D. that

[填空题]Most theories about the evolution of Earth have the same general point of view.

[单项选择]One of the many theories about alcoholism is the learning and reinforcement theory, which explains alcoholism by considering alcohol drinking as a reflex response to some stimulus and as a way to reduce an inner drive state such as fear or anxiety. Characterizing life situations in terms of approach and avoidance, this theory holds that persons tend to be drawn to pleasant situations or repelled by unclean, sanity ones. In the latter case, alcohol drinking is said to reduce the tension or feelings of unpleasantness and to replace them with the feeling of pleasure generally observed in most persons after they have consumed one or more drinks.
Some experimental evidence tends to show that alcohol reduces fear in an approach-avoidance situation. Conger trained one group of rats to approach a food goal and trained another group to avoid electric shock. After an injection of alcohol the pull away from the shock was measurably weaker, while the pull toward food was unchanged.
The o
A. the learning theory contradicts itself in some fields.
B. drinking alcohol can solve the problem of family discord.
C. tension reduction appears first after drinking alcohol.
D. the unpleasant consequence of alcoholism can make alcoholics stop drinking.

[单项选择]Many theories have been ______ as to why some women suffer from depression.
A. referred to
B. put forward
C. rest assured
D. left out

[填空题]Many cultures have different ideas about why people catch colds. For example, in the United States, some people think that you can catch cold if your (1) get cold. So, mothers tell little children to wear (2) boots in the winter. In other places, including parts of the Middle East, some people believe that strong winds cause colds. So, on trains and buses, people usually don’t like to sit (3) open windows. In parts of Europe, some people think that wearing wet clothes will give you a cold. They say that after you go (4) , you should quickly put on dry clothes. Today, scientists know that colds are caused by viruses. But the old ideas are still very strong, and many people still follow them to (5) getting ill.Many cultures have different ideas about why people catch colds. For example, in the United States, some people think that you can catch cold if your (1) get cold. So, mothers tell little children to wear (2)