The innate tendency of human cells to self-destruct, the clocklike changes in some hormones, and the decline of effectiveness of the human immune system are all factors that lend support to ____ theories of aging

What is meant by an "obsession"?

a. A fear that interferes with everyday life b. A repetitive, unwanted thought c. A repetitive, almost irresistible action d. A belief that is strongly held despite a lack of evidence for it

H0 is to Ha as _____ hypothesis is to _____ hypothesis

a. null; alternative b. alternative; null c. one-tailed; two-tailed d. two-tailed; one-tailed