Which of the Following Statements Is True About the Effects

Which of the following statements is true about the effects of aging on the pulmonary system?
1) Alveolar septa gradually deteriorate.
2) The number of alveoli gradually decreases.
3) Loss of alveolar walls reduces the surface area for gas exchange.
4) Smooth muscle fibers in the lungs are progressively replaced with fibrous connective tissue.

A) 1 and 3
B) 2 and 4
C) 1, 2, and 3
D) 1, 3, and 4