填空题
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．the auctioneer knocks the buyer down B．the auctioneer knocks the rostrum down C．the goods are knocked down on to the table D．the auctioneer bangs the table with a hammer