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【单选题】

Space is a erous place, not only because of meteors but also because of rays from the Sun and other stars.
Radiation is the greatest known er to explorers in space. Doses of radiation are measured in units called "rem". We all receive radiation here on the Earth from the Sun, from cosmic rays and from radioactive minerals. The "normal" dose of radiation that we receive each year is about 100 millirem; it varies according to where you live, and this is a very rough estimate. Scientists have reason to think that a man can put up with far more radiation than this without being damaged; the figure of 60 rein has been agreed on. The trouble is that it is extremely difficult to be sure about radiation damage—a person may feel perfectly well, but the cells of his or her organs may be damaged, and this will not be discovered until the birth of children or even grandchildren.
Early space probes showed that radiation varies in different parts of space around the Earth. It also varies in time because, when great spurts of gas shoot out of the Sun, they are accompanied by a lot of extra radiation. Some estimates of the amount of radiation in space, based on various measurements and calculations, are as low as 10 rem per year, while others are as high as 5 rem per hour! Mission to the Moon have had to cross the Van Allen belts of high radiation and, during the outward and return journeys, the Apollo 8 crew accumulated a total dose of about 200 millirem per man. It was hoped that there would not be any large solar flares during the times of Apollo moon walks because the walls of the lunar excursion modules (LEMs) were not thick enough to protect the men inside, though the command modules did give reasonable protection. So far, no erous doses of radiation have been reported, but the Gemini (双子座) orbits and the Apollo missions have been quite short. We simply do not know yet how men are going to get on when they spend weeks and months outside the protection of the atmosphere, working in a space laboratory or in a base on the Moon. Drugs might help to decrease the damage done by radiation, but no really effective ones have been found so far. At present, radiation seems to be the greatest physical hazard to space travelers, but it is impossible to say just how serious the hazard will turn out to be in the future. What make space a erous place

A.
The radioactive meteors.
B.
The Sun and other stars.
C.
Rays from the Earth.
D.
Rein.
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参考答案:
举一反三

【单选题】双子座流星雨的辐射点位于( )附近

A.
北河二
B.
北河三
C.
天猫与双子交界
D.
御夫与双子交界

【单选题】狮子座流星雨与哪颗彗星有关()。

A.
谭普-塔特尔彗星(CometTemple-TuttlE.
B.
斯威夫特-塔特尔彗星(CometSwift-TuttlE.
C.
池-谷关彗星(CometIkeya-Saki)
D.
比拉彗星(3D/BielA.

【单选题】狮子座流星雨得名的缘由是______。

A.
所有的流星都来自狮子座
B.
其发现者就是狮子座的命名者
C.
流星雨的方位与狮子座在天球上的投影相重叠
D.
发生于每年7月23日至8月22日,即狮子座入主黄道期间
相关题目:
【单选题】双子座流星雨的辐射点位于( )附近
A.
北河二
B.
北河三
C.
天猫与双子交界
D.
御夫与双子交界
【单选题】狮子座流星雨与哪颗彗星有关()。
A.
谭普-塔特尔彗星(CometTemple-TuttlE.
B.
斯威夫特-塔特尔彗星(CometSwift-TuttlE.
C.
池-谷关彗星(CometIkeya-Saki)
D.
比拉彗星(3D/BielA.
【单选题】狮子座流星雨得名的缘由是______。
A.
所有的流星都来自狮子座
B.
其发现者就是狮子座的命名者
C.
流星雨的方位与狮子座在天球上的投影相重叠
D.
发生于每年7月23日至8月22日,即狮子座入主黄道期间
【单选题】狮子座中最亮的一颗星叫什么?()
A.
轩辕十三
B.
心宿二
C.
轩辕十四
D.
角宿一
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