**Core Concept**
Physiological atrophy refers to the reduction in size of a muscle or organ due to disuse or decreased demand. This type of atrophy is reversible and occurs when the muscle or organ is not functioning at its usual level, such as in the case of immobilization or denervation.

**Why the Correct Answer is Right**
Physiological atrophy is characterized by the breakdown of muscle fibers and a decrease in protein synthesis. This leads to a reduction in muscle mass and strength. The process is reversible, and muscle function can be restored once the muscle is used again. The key enzymes involved in this process include caspases, which are responsible for the breakdown of muscle fibers, and mTOR (mechanistic target of rapamycin), which regulates protein synthesis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because pathological atrophy is a permanent loss of muscle mass and function due to disease or injury, whereas physiological atrophy is reversible.
**Option B:** This option is incorrect because muscle hypertrophy refers to the increase in size of a muscle due to exercise or increased demand, which is the opposite of physiological atrophy.
**Option C:** This option is incorrect because muscle atrophy due to disuse is a specific type of physiological atrophy, but it is not the only example.

**Clinical Pearl / High-Yield Fact**
Physiological atrophy can occur in any muscle or organ that is not functioning at its usual level, and it is reversible with the restoration of normal function. This is an important consideration in the management of patients with immobilization or denervation injuries.

**Correct Answer: C. Muscle atrophy due to disuse is an example of physiological atrophy.**