题目内容
Another theory proposes that the ancestral home of all modern birds was the tropics. When the region became overpopulated, many species were crowded north. During the summer, there was plenty of food, but during the winter, scarcity forced them to return to the tropics.
A more recent theory, known as photoperiodism, suggests a relationship between increasing daylight and the stimulation of certain glands in the birds' bodies that may prepare them for migration. One scientist has been able to cause midwinter migrations by exposing birds to artificial periods of daylight. He has concluded that changes occur in the bodies of birds due to seasonal changes in the length of daylight.
According to one theory, when the glaciers disappeared, birds ______. ()
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W: But my English isn't good enough to act in a play.
Q: What does the woman mean？
(19)
To squeeze the most out of each shining hour we have shortened the opera, quickened the pace of the movie and put culture in pocket-sized packages. We make the busy bee look like a lazy creature, the ant like a sluggard. We live sixty-mile-minute and the great efficiency smiles.
We wish we could return to that pleasant day when we considered time a friend instead of an enemy; when we did things willingly and because we wanted to, rather than because our timetable called for it, But that of course would not be efficiency; and we Americans must be efficient.
The phrase that best expresses the main idea of this passage is ______. ()
Of course sometimes there were real disasters which attracted the attention of governments and which showed need for changes. Also scientists who were doing research into the health of workers sometimes produced information which governments could not ignore. At such times, there were inquiries into the causes of the disaster or the problems. New safety rules were often introduced as a result of these inquiries; however, the new rule; came too late to protect the people who died or who became seriously ill.
Today many governments have special departments which protect customers and workers. In the U.S., for example, there is a department which tests new airplanes and gives warnings about possible problems. It also makes the rules that aircraft producers must follow. Another department controls the foods and drugs that companies sell. A third department looks at the places where people work, and then reports any companies that are breaking laws which protect the health and safety of workers. Of course, new government departments and new laws cannot prevent every accident or illness, but they are having some good results. Our work places are safer and cleaner than before. The planes and cars which we use for travel are better. Producers are thinking more about the safety and health of the people who buy and use their products.
The main topic of the passage is ______. ()
A．He's already helped her a lot.B．She knows he's very busy.C．She doesn't need any help
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