[单选题]
A nuclear reaction is q tgfh ngb-:)n o9-4v(f zsfu 9a3hr;abjm f(e1qy6ah-n*bl0o 9 grl(said to be endothermic if the total kinetic energy is
A. less after the reaction than before.
B. equal both before and after the reaction.
C. greater after the reaction than before.
D. zero after the reaction.