单项选择题

What is the distance between the Earth and the two areas of radiation

A．Between 12 and 21 miles
B．1,000 miles
C．150 miles
D．1,500 miles
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单项选择题
Why can't people on earth be harmed by radiation
A．Because men on the Earth are protected by the atmosphere.
B．Because radiation only has short-term effects on men on the Earth.
C．Because there is a great distance between the Earth and the radiation areas.
D．Because the Van Allen Belts absorb all radiation.
单项选择题
What forms of radiation are feared by astronauts
A．Radiation from the sun.
B．Radiation from the Van Allen Belts.
C．Radiation from the meteors.
D．Both Ａ and Ｂ.
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