单项选择题
A．exposure to even tiny amounts of radiation is fatal B．the effect of exposure to radiation is slow in coming C．radiation is avoidable in space exploration D．astronauts in spacesuits needn't worry about radiation damage
A．a very great English novel B．an accurate portrayal of life in wartime C．an excellent piece of satire D．the work of a neglected author
A．is insignificant B．is enormous C．seems overestimated D．remains unknown