The human immunodeficiency virus has been found to be the cause of

Perry works at a job where he is paid by commission. For every car Perry sells, he gets 10 percent of the profits. Perry is being reinforced on a ______

a. fixed-ratio schedule c. variable-ratio schedule b. fixed-interval schedule d. variable-interval schedule

Freud modified his theory of sexual abuse when he realized that:

a. Many of his female clients were lying about the abuse they said they suffered. b. Sexual abuse had little impact on his female clients' adjustment as adults. c. The medical community rejected his original theory. d. Sexual abuse was generally harmless to children. e. The alleged abusers were respectable citizens.