Older people are more likely to develop autoimmune diseases. One possibility is

Older people are more likely to develop autoimmune diseases. One possibility is
  a. a heightening of the immune response associated with age.
  b. an increase in the number of T cells.
  c. an increase in the activity of B cells.
  d. a reduction in DNA repair mechanisms leading to a change in self-markers.
  e. viral infections.

Question 2

Age-related changes in systems other than the nervous system include
  a. a decrease in the size of the heart.
  b. a break down of alveolar walls in the lungs.
  c. the buildup of cholesterol plaques in blood vessels.
  d. a decrease in blood transport to organs.
  e. all of these.