**Core Concept**
Aerobic capability refers to the body's ability to utilize oxygen to generate energy through the process of oxidative phosphorylation. This process is crucial for high-intensity, long-duration activities that require sustained energy production.

**Why the Correct Answer is Right**
The correct answer is related to the concept of mitochondrial density and myoglobin content in muscle cells. Myoglobin is a protein that stores oxygen in muscles, allowing for a higher capacity for aerobic respiration. Mitochondrial density, on the other hand, refers to the number of mitochondria present in muscle cells, which are the site of oxidative phosphorylation. Increasing mitochondrial density and myoglobin content in muscle cells enhances the body's aerobic capability, allowing for more efficient energy production during high-intensity activities.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because increasing muscle glycogen stores, while important for anaerobic energy production, does not directly enhance aerobic capability.
**Option B:** This option is incorrect because increasing hemoglobin content in red blood cells, while improving oxygen delivery to tissues, does not directly enhance aerobic capability within muscle cells.
**Option C:** This option is incorrect because increasing muscle fiber size, while important for overall muscle strength, does not directly enhance aerobic capability.

**Clinical Pearl / High-Yield Fact**
To maximize aerobic capability, focus on increasing mitochondrial density and myoglobin content in muscle cells through regular aerobic exercise, such as running or cycling, and a balanced diet rich in antioxidants and other essential nutrients.

**Correct Answer:** C. Increasing muscle fiber size through resistance training can indirectly enhance aerobic capability by improving muscle efficiency, but this is not the most direct method of increasing aerobic capability.