If adult male chimpanzee A grooms adult male chimpanzee B, which of the following events would be consistent with the theory of reciprocal altruism?
a) Chimpanzee A expects grooming in return
b) Chimpanzee B reciprocates the grooming
c) Chimpanzee B refuses to groom Chimpanzee A
d) Chimpanzee A steals food from Chimpanzee B