The harm radiation has done to the Apollo crew members ______.

A．the Apollo mission was very successful
B．protection from space radiation is not a easy job
C．astronauts will have deformed children or grandchildren
D．radiation is not a threat to well-protected space explorers

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 spacesuit needn't worry about radiation damage