**Core Concept**
At high altitudes, the partial pressure of oxygen in the air is lower, leading to a decrease in oxygen delivery to the muscles. This results in a decrease in work capacity due to inadequate oxygen supply. To adapt to this environment, the human body makes various physiological changes to increase oxygen delivery and utilization.

**Why the Correct Answer is Right**
Decreasing workload and increasing duration of exercise is an apt adaptation to high altitude because it allows the body to conserve energy and utilize oxygen more efficiently. By reducing the intensity of exercise, the body requires less oxygen, which is scarce at high altitudes. At the same time, increasing the duration of exercise allows the body to adapt to the lower oxygen levels by increasing red blood cell production, improving oxygen delivery to the muscles, and enhancing the body's ability to utilize oxygen.

**Why Each Wrong Option is Incorrect**
**Option A:** Increasing workload and decreasing duration of exercise would exacerbate the problem of inadequate oxygen supply, leading to premature fatigue and decreased work capacity.
**Option B:** Increasing workload and increasing duration of exercise would require even more oxygen, which is not available at high altitudes, resulting in further decreased work capacity.
**Option D:** Decreasing workload and decreasing duration of exercise would not help the body adapt to high altitude, as it would not stimulate the necessary physiological changes to increase oxygen delivery and utilization.

**Clinical Pearl / High-Yield Fact**
At high altitudes, the body's ability to adapt to low oxygen levels is crucial for increasing work capacity. This can be achieved by increasing red blood cell production, improving oxygen delivery to the muscles, and enhancing the body's ability to utilize oxygen. A commonly used adaptation strategy is to ascend to high altitude gradually, allowing the body to acclimate to the lower oxygen levels.

✓ Correct Answer: C. Decreasing workload, increasing duration of exercise