[单选题]
A nuclear reaction is said to b un2dk 4wvccu+g:pr*b2e31xae ei- 6jdc 8pnse z(hhb07xothermic 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.