Through what means did researchers discover the characteristics of two major types of sleep?

Which of the following is true?

a. Someone who is exposed to the cold virus is almost certainly going to come down with a cold. b. For people with serious diseases such as cancer, it doesn't matter how much control they feel they have over the disease or its consequences. c. If a college student experiences one or more of the stressful life events at the top of the College Life Stress Inventory, he or she will almost certainly get sick. d. Many people who experience the death of a loved one do not experience severe distress and recover quickly.

Laura is 45 years old, and her husband Shane is 48 years old. They already have a child and want to have another child. Their physician states that their chances of conceiving a child are extremely low. Which of the following is the most likely reason for this reduced ability to bear children?

A. Shane has a very high sperm count. B. Laura and Shane are genetically incompatible. C. Laura and Shane are not from the same ethnicity. D. Laura is too old to bear children.