Questions 31 to 35 are based on the following passage:

　　The great advance in rocket theory 40 years ago showed that liquid—fuel rocket were far superior in every respect to the skyrocket with its weak solid fuel, the only kind of rocket then known. However, during the last decade, large solid—fuel rockets with solid fuels about as powerful as liquid—fuels have made their appearance, and it is a favorite layperson's question to inquire which one is better. The question is meaningless; one might as well ask whether a gasoline or a diesel engine is better. It all depends on the purpose. A liquid—fuel rocket is complicated, but has the advantage that it can be controlled beautifully. The burning of the rocket engine can be stopped completely; it can be re—ignited when desired. In addition, the thrust can be made to vary by adjusting the speed of the fuel pumps. A solid—fuel rocket, on the other hand, is rather simple in construction, though hard to build when a really large size is desired. But once you have a solid—fuel rocket, it is ready for action at very short notice. A liquid—fuel rocket has to be fueled first and cannot be held in readiness for very long after it has been fueled. However, once a solid—fuel rocket has been ignited, it will keep burning. It cannot be stopped and re—ignited whenever desired (it could conceivably be stopped and re—ignited after a pre—calculated time of burning has elapsed) and its thrust cannot be varied. Because a solid—fuel rocket can be kept ready for a long time, most military missiles employ solid fuels, but human—piloted space flight needs the fine adjustments that can only be provided by liquid fuels. It may be added that a liquid—fuel rocket is an expensive device; a large solid—fuel rocket is, by comparison, cheap. But the solid fuel, pound per pound, costs about 10 times as much as the liquid fuel. So you have, on the one hand, an expensive rocket with a cheap fuel and on the other hand a comparatively cheap rocket with an expensive fuel.

　　31. Which of the following is implied in the passage?

　　A. Rockets using liquid fuel was not available 40 years ago although researches were being done on the practicability of using liquid fuel in rockets.

　　B. It was not until the last decade that rockets using solid fuels made their appearance.

　　C. Complicated rockets using solid fuel have the advantage of flexibility and adjustability that liquid—fuel rockets don't possess.

　　D. Liquid fuel costs about 10 times as much as the solid fuel costs.

　　32. Which of the following was NOT mentioned as one of the advantages of liquid?fuel rockets?

　　A. They are easy to control. B. Their thrust is variable.

　　C. They are easy to construct. D. Their speed is adjustable.

　　33. Solid—fuel rockets are expensive to operate because of their .

　　A. burning time B. size C. fuel D. engines

　　34. The chief consideration for using liquid fuels in human—piloted space flights is that the rocket .

　　A. is inexpensive to construct B. is capable of carrying heavy cargo

　　C. is easy to control D. is inexpensive to operate

　　35. Which of the following statements is true about solid—fuel rockets?

　　A. They are simple to construct.

　　B. They can be re—ignited when desired.

　　C. They can provide fine adjustments in operation.

　　D. They cost a lot less than liquid—fuel rockets to construct.

　　Questions 36 to 40 are based on the following passage:

　　For some time past it has been widely accepted that babies—and other creatures—learn to do things because certain acts lead to rewards; and there is no reason to doubt that this is true. But it used also to be widely believed that effective rewards, at least in the early stages, had to be directly related to such basic physiological drives as thirst or hunger. In other words, a baby would learn if he got food or drink or some sort of physical comfort, not otherwise.

　　It is now clear that this is not so. Babies will learn to behave in ways that produce results in the world with no reward except the successful outcome.

　　Papousek began his studies by using milk in the normal way to reward the babies and so teach them to carry out some simple movements, such as turning the head to one side or the other. Then he noticed that a baby who had had enough to drink would refuse the milk but would still go on making the learned response in situations where no milk was provided. He quickly found that children as young as four months would learn to turn their heads to right or left if the movement switched on a display of lights— and indeed that they were capable of learning quite complex turns to bring about this result, for instance, two left or two right, or even to make as many as three turns to one side.

　　Papousek's light display was placed directly in front of the babies and he made the interesting observation that sometimes they would not turn back to watch the lights closely although they would smile and bubble when the display came on. Papousek concluded that it was not primarily the sight of the lights which pleased them, it was the success they were achieving in solving the problem, in mastering the skill, and that there exists a fundamental human urge to make sense of the world and bring it under intentional control.

　　36. In this article, the author suggests that babies learn to do things when

　　A. such acts lead to desired rewards

　　B. they enjoy a sense of achievement

　　C. their curiosity is satisfied

　　D. they can derive fun from such acts

　　37. In his experiment, Papousek noticed that a baby

　　A. would go on making the learned response with no milk provided

　　B. would have to have enough to drink before the experiment began

　　C. would not make the learned response until milk is provided

　　D. would make the learned response with pleasure only when it saw the light display

　　38. According to the passage, the babies would smile and bubble when the light display was turned on primarily because

　　A. the babies were impressed by the beautiful sight

　　B. the lights are related to babies' physical drives

　　C. the babies felt they succeeded in switching on the lights

　　D. the babies were happy that they learned how to respond to this sight

　　39. According to Papousek, the pleasure the babies displayed when they saw the light display was a reflection of

　　A. the satisfaction of their curiosity

　　B. the satisfaction of their physiological needs

　　C. the basic human urge to understand and control the world

　　D. the babies' desire to solve complex problems

　　40. What does the word “it” in the last line refer to?

　　A. success B. skill C. light D. world

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