Question

20．As in the field of space travel，new technologies continue to appear in undersea exploration．They share a number of similarities with each other-as well as some important differences．
Manned submersibles （潜水器），like spaceships，must maintain living conditions in an unnatural environment．While a spaceship must simply be sealed against the vacuum space，a submersible must be able to bear extreme pressure if it is not to break up in deep water．
In exploring space，unmanned vehicles were employed before astronauts．In undersea exploration，on the other hand，men paved the way，and only recently have unmanned remote-operated vehicles （ROVs） been put to use．
One reason for this is that communicating with vehicles in orbit is much easier than talking to those underwater．A vacuum is an ideal medium for radio communications，but underwater communications are limited to much slower sound waves．Thus，most undersea vehicles-particularly ROVs-operate at the end of long ropes．（电缆终端）
For a similar reason，knowing where you are undersea is much more difficult than in space．A spaceship's position can be located by following its radio signal，or by using telescopes and radar．For an undersea vehicle，however，a special network of sonar （声纳系统）devices must be laid out in advance on the ocean floor in the area of a dive to locate the vehicle's position．
Though undersea exploration is more challenging than outer space in a number of respects，it has a distinct advantage：going to the ocean depths doesn't require the power necessary to escape Earth's gravity．Thus，it remains far less expensive．
64．The purpose of the passage isD
A．to persuade you to explore the depths of the ocean
B．to stress the importance of the undersea exploration
C．to make you believe that the undersea exploration is better
D．to tell some differences between two kinds of explorations 
65．By saying"men paved the way"in Paragraph 2 the author means that in undersea explorationC．
A．unmanned vehicles were used in the beginning
B．men covered the ocean floor with stones and bricks
C．manned vehicles were employed before unmanned ones      
D．men invented unmanned remote-operated vehicles in the past
66．The sonar devices must be placedC．
A．from time to time               
B．after the undersea vehicles dive
C．before the undersea vehicles dive
D．when the undersea vehicles are diving
67．What can we infer from the passage？C
A．Submersibles usually break up in deep water．
B．Undersea vehicles can receive signals immediately．
C．Going to space needs power to escape the gravity．
D．Radio communications are quite difficult in a vacuum．

Answer 1

分析 本文属于说明文阅读，作者通过这篇文章主要向我们描述了从两种探索的环境、通讯速度、位置的确定及成本的高低等不同方面来比较探索太空和探索海底世界的不同．

解答 64．D．写作目的题．文章首段点出文章的中心．通读全文可知，文章从两种探索的环境、通讯速度、位置的确定及成本的高低等不同方面来比较探索太空和探索海底世界的不同；故选D．
65．C．句意理解题．上文提到科学家探索太空时先用无人太空船试验，之后才用载人太空船；由关键短语on the other hand 及下文提到的无人潜水器最近才被使用可推知此处指探索海底不同于探索太空，是先用载人潜水器的；故选C．
66．C．细节理解题．由倒数第二段最后一句a special network of sonar （声纳系统）devices must be laid out in advance on the ocean floor in the area of a dive to locate the vehicle's position可知利用声波探测水下物体的装置是在探索之前置于海底的；故选C．
67．C．推理判断题．文中第一段提到潜水器必须能承受极大的水压，并非指潜水器在深水处通常会被毁坏，故A项不正确；由第三段可知信号在水中传输速度慢，故B项不正确；由第三段中A vacuum is an ideal medium 可知D项不正确；最后一段指出探索海底有一个隐含的优点：不需要摆脱地球引力的能量，所以成本较探索太空稍低，由此可知，探索太空需要摆脱地球引力的能量；故选C．

点评 考察学生的细节理解和推理判断能力，做细节理解题时一定要找到文章中的原句，和题干进行比较，再做出正确的选择．在做推理判断题不要以个人的主观想象代替文章的事实，要根据文章事实进行合乎逻辑的推理判断．