According to Darwin, facial expressions probably evolved to help us communicate our emotional states to others and provoke a response from them. This signaling function begins in __________

Anything that follows a response, making that response more likely to recur, is __________

a. an antecedent b. an enhancement c. reinforcement d. consequence

One parent can produce about ___ different combinations of chromosomes, and the two together can produce about ___

a. 8 million, 60 to 70 trillion b. 100 million, 250 trillion c. 2 billion, 750 trillion d. 1 million, 6 trillion