The best title for this passage would be ______.

A．the Apollo mission was very successful
B．protection from space radiation is no easy job
C．astronauts will have deformed children or grandchildren
D．radiation is not a threat to well-protected space explores

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 space suits needn't worry about radiation damage