首页
登录
职称英语
As in the field of space travel, so in undersea exploration new technologies con
As in the field of space travel, so in undersea exploration new technologies con
游客
2023-07-18
46
管理
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.(潜水器), 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 deep water.
In exploring space, unmanned vehicles were employed before astronauts. In undersea exploration, on the other haled, men paved (铺路) 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 process.
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) devices most 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 doesn’t require the power necessary to escape Earth’s gravity. Thus, it remains far less expensive. [br] The sonar devices must be placed ______.
选项
A、before the undersea vehicle dives
B、at the time when the undersea vehicle is diving
C、from time to time
D、after the undersea vehicle dives
答案
A
解析
见第五段第3句,原文在论述这一问题时用的状语是in advance,意为“预先”,也就是说在事前需安装好, 所以A)项为正确答案
转载请注明原文地址:https://tihaiku.com/zcyy/2848167.html
相关试题推荐
______(由于航空公司间激烈的竞争),travelexpenseshavebeenreducedconsiderably.Owingtofi
TipsforTravelingAloneWhenitcomestotraveling,so
TipsforTravelingAloneWhenitcomestotraveling,so
TipsforTravelingAloneWhenitcomestotraveling,so
TipsforTravelingAloneWhenitcomestotraveling,so
TipsforTravelingAloneWhenitcomestotraveling,so
FrequentbusinesstravelerJoyceGioiaforgotmorethan$20000worthofje
FrequentbusinesstravelerJoyceGioiaforgotmorethan$20000worthofje
FrequentbusinesstravelerJoyceGioiaforgotmorethan$20000worthofje
FrequentbusinesstravelerJoyceGioiaforgotmorethan$20000worthofje
随机试题
【B1】[br]【B4】A、withB、withoutC、outB后面分句中的"without"一词与这个空格对应。
Aresearcherdiscoveredthatpeoplewhohavelowlevelsofimmune-systemactivit
[originaltext]M:Carol,doyouknowwhenProf.Wang’sChineseLiteratureFinal
对于AdobeAudition音频处理软件,设臵某个音频片段音量大小随时间而变化
以行政强制行为的目的和程序的阶段性为标准可以将行政强制分为( )。A.即时性强
关于献血后护理的指导以下哪种描述正确( )。A.用餐时过量饮酒 B.献血当天
一键顺控生成任务的试验内容包括:权限校验、()、添加多个操作任务。(A)
神经衰弱症患者的呼吸节律特点是 A.Kussmaul呼吸B.Cheyn
商品市场的需求量通常由()组成。A.前期库存量 B.期末商品结存量 C
(2017年真题)为使监理工作得到有关各方的理解与支持,编写监理规划时应充分听取
最新回复
(
0
)