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 （潛水器），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．（電纜終端）
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 （聲納系統(tǒng)）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．a(chǎn)fter 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 本文屬于說(shuō)明文閱讀，作者通過(guò)這篇文章主要向我們描述了從兩種探索的環(huán)境、通訊速度、位置的確定及成本的高低等不同方面來(lái)比較探索太空和探索海底世界的不同．

解答 64．D．寫(xiě)作目的題．文章首段點(diǎn)出文章的中心．通讀全文可知，文章從兩種探索的環(huán)境、通訊速度、位置的確定及成本的高低等不同方面來(lái)比較探索太空和探索海底世界的不同；故選D．
65．C．句意理解題．上文提到科學(xué)家探索太空時(shí)先用無(wú)人太空船試驗(yàn)，之后才用載人太空船；由關(guān)鍵短語(yǔ)on the other hand 及下文提到的無(wú)人潛水器最近才被使用可推知此處指探索海底不同于探索太空，是先用載人潛水器的；故選C．
66．C．細(xì)節(jié)理解題．由倒數(shù)第二段最后一句a special network of sonar （聲納系統(tǒng)）devices must be laid out in advance on the ocean floor in the area of a dive to locate the vehicle's position可知利用聲波探測(cè)水下物體的裝置是在探索之前置于海底的；故選C．
67．C．推理判斷題．文中第一段提到潛水器必須能承受極大的水壓，并非指潛水器在深水處通常會(huì)被毀壞，故A項(xiàng)不正確；由第三段可知信號(hào)在水中傳輸速度慢，故B項(xiàng)不正確；由第三段中A vacuum is an ideal medium 可知D項(xiàng)不正確；最后一段指出探索海底有一個(gè)隱含的優(yōu)點(diǎn)：不需要擺脫地球引力的能量，所以成本較探索太空稍低，由此可知，探索太空需要擺脫地球引力的能量；故選C．

點(diǎn)評(píng) 考察學(xué)生的細(xì)節(jié)理解和推理判斷能力，做細(xì)節(jié)理解題時(shí)一定要找到文章中的原句，和題干進(jìn)行比較，再做出正確的選擇．在做推理判斷題不要以個(gè)人的主觀想象代替文章的事實(shí)，要根據(jù)文章事實(shí)進(jìn)行合乎邏輯的推理判斷．