**Core Concept**
With aging, the lungs undergo changes that affect their mechanical properties and function. Pulmonary compliance, a measure of the lung's ability to expand and fill with air, is influenced by the elastic properties of the lung tissue and the chest wall.

**Why the Correct Answer is Right**
As people age, the lungs undergo a process called elastosis, where the elastic fibers in the lung tissue break down and become less flexible. This results in a decrease in the elastic recoil of the lungs, making it easier for them to expand and fill with air. Additionally, the chest wall becomes less rigid with age, further contributing to the increase in pulmonary compliance. This allows older adults to exhale more slowly and take in more air during inhalation, compensating for the decreased lung function.

**Why Each Wrong Option is Incorrect**
**Option B:** Residual volume actually increases with age due to the loss of lung elasticity and the downward movement of the diaphragm. This makes it more difficult for older adults to exhale completely.
**Option C:** Mucociliary clearance, the process by which mucus and debris are cleared from the airways, actually decreases with age. This makes older adults more susceptible to respiratory infections.
**Option D:** Alveolar dead space, the volume of air in the lungs that does not participate in gas exchange, actually increases with age due to the loss of lung elasticity and the formation of scar tissue.

**Clinical Pearl / High-Yield Fact**
As a general rule, lung function decreases with age, but the rate and extent of this decline can be influenced by factors such as smoking, physical activity, and overall health.

✓ Correct Answer: **A.** Pulmonary compliance increases