首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
As in the field of space travel, so in undersea exploration new technologies continue to appear. They share a number of similari
As in the field of space travel, so in undersea exploration new technologies continue to appear. They share a number of similari
admin
2014-03-03
34
问题
As in the field of space travel, so in undersea exploration new technologies continue to appear. They share a number of similarities with each other--as well as some important differences.
Manned submersibles, like spaceships, must maintain living conditions in an unnatural environment. But while a spaceship must simply be sealed against the vacuum of space, a submersible must be able to bear extreme pressure if it is not to break up in the 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 re- mote-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.
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 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 aspects, 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.
People did not begin to use unmanned vehicles in undersea exploration until recently because of______.
选项
A、the communication problem
B、the movement of waves
C、the ocean depths
D、the problem of vacuum
答案
A
解析
就为什么“人们直到最近才开始在海底探索中使用无人驾驶的遥控装置”这一问题,作者在第四段开头和第五段开头明确地给出了原因:“one reason for this is communicating with vehicles in orbit is much easier than talking to those underwater”及“For a similar reason, knowing where you are undersea is much more difficult than in space”。因此可以断定[A]是正确答案。
转载请注明原文地址:https://kaotiyun.com/show/GbpO777K
0
专业英语八级
相关试题推荐
Today,therearemanyavenuesopeningtothosewhowishtocontinue1.______theireducation.However,nearlyallrequiresomeb
Themajorityofcountriesintheworldspendlargeamountsofmoneydevelopingweaponstodefendthemselvesthoughtheyarenot
ThereisagreatemploymentdemandforgraduatesofallthefollowingmajorsEXCEPT
TheEuropeanUnionhadapprovedanumberofgeneticallymodifiedcropsuntillate1998.Butgrowingpublicconcernovertheir
TheEuropeanUnionhadapprovedanumberofgeneticallymodifiedcropsuntillate1998.Butgrowingpublicconcernovertheir
AccordingtoDeirdreImus,whyisitimportanttoraisegreenkids?
AccordingtoDeirdreImus,whyisitimportanttoraisegreenkids?
Inrecentyears,manyfamousuniversitiesloweradmissionrequirementsforcelebrities.Moreandmorecelebrities,especiallysp
Thebizarreanticsofsleepwalkershavepuzzledpolice,perplexedscientists,andfascinatedwritersforcenturies.Thereisan
你知道中国最有名的人是谁?提起此人,人人皆晓,处处闻名。他姓差,名不多,是各省各县各村人氏。你一定见过他,一定听过别人谈起他。差不多先生的名字天天挂在大家的口头,因为他是中国全国人的代表。差不多先生的相貌和你和我都差不多。他有一双眼睛
随机试题
岗位的质量保证措施与责任就是岗位的质量要求。
以下不属于心的阳气虚衰的表现是
下列各项中不属于传染病基本特征的是
患儿,男,6岁,因风湿热入院,使用阿司匹林和青霉素进行治疗。近3天该患儿出现了食欲不振、恶心呕吐等胃肠道症状,护士给予的指导正确的是
根据我国《民事诉讼法》及相关司法解释的有关规定,下列哪些案件法院应受理?()
某企业12月份发生下列有关存货的经济业务:(1)12月1日,购入A材料50千克,每千克100元,计价款5000元,增值税进项税额850元,均已用银行存款支付,材料尚未到达。(2)12月5日,购入B材料200千克,每千克400元,计价款80000元,增值
()是商王朝由衰落走向中兴的一个转折点。
随着互联网的发展,人们的购物方式有了新的选择。很多年轻人喜欢在网络上选择自己满意的商品,通过快递送上门,购物足不出户,非常便捷。刘教授据此认为,那些实体商城的竞争力会受到互联网的冲击,在不远的将来,会有更多的网络商店取代实体商店。以下哪项如果为真,最能削弱
顾某欲与闫某离婚。下列情形中,顾某既可以之作为起诉离婚的理由,同时可请求损害赔偿的有()。
【M1】"Therewereasetofideasandasetofinitiativesthattheuniversityisundertakingthatpeoplewantedtoinvest,"saidM
最新回复
(
0
)