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Being alone in outer space can be frightening. That is one reason why astronauts on solo (单独的) space flights were given plenty of work to keep them 21 . They were also constant communication with people on the earth. 22 , being with people from whom you cannot get away might be even harder than being alone. This is what happens on long submarine (潜水艇) voyages. It will also happen on 23 space flights in the future. Will there be special problem of adjustment under such conditions?
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