Which of the following is true、

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• 1When men spend long periods in space how will they protect themselves、

  A.By taking special drugs.

  B.By wearing special suits.

  C.By using a protective blanket.

  D.No solution has been found yet.

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• 2The spacemen were worried about solar flares when they were

  A.crossing the Van Allen belts.

  B.setting up a moon base.

  C.exploring the surface of the moon.

  D.waiting in the command modul

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• 3Scientists have fixed a safety level of

  A.10 rems per year.

  B.60 rems per year.

  C.100 millirems per year.

  D.5 rems per hour.

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• 4The worst hazard for spacemen is

  A.meteors.

  B.heat.

  C.radiation.

  D.gas.

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• 5In sentense 2,“speculated on”(line 4)means

  A.suspected

  B.expected

  C.engaged in buying and selling

  D.considered

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