It is much easier for a small animal to run uphill than for a large animal, because:

Options

A. The efficiency of muscles in large animals is less than in the small animal
B. It is easier to carry a small body weight
C. Small animals have a higher metabolic rate
D. Small animals have a lower O2 requirement.

Answer

To solve the question of why it is much easier for a small animal to run uphill than for a large animal, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks why small animals find it easier to run uphill compared to large animals. This implies we need to consider factors such as body weight, metabolic rate, and energy expenditure.

2. **Analyzing the Options**: The options provided include:
- A) The efficiency of muscles in large animals is less than in small animals.
- B) It is easier to carry a small body weight.
- C) Animals have a higher metabolic rate.
- D) Small animals have lower oxygen requirements.

3. **Evaluating Each Option**:
- **Option A**: This option suggests that larger animals have less efficient muscles. However, muscle efficiency does not solely determine the ability to run uphill.
- **Option B**: While it is true that smaller animals have less body weight to carry, this alone does not explain the ease of running uphill.
- **Option C**: This option states that small animals have a higher metabolic rate. This is a crucial point because a higher metabolic rate means they can generate energy more quickly, which is beneficial for activities like running uphill.
- **Option D**: This option claims that small animals have lower oxygen requirements. However, metabolic processes in small animals often require more oxygen relative to their size due to their higher metabolic rates.

4. **Identifying the Correct Answer**: After evaluating the options, we find that the most valid reason is **Option C**: small animals have a higher metabolic rate. This higher metabolic rate allows them to utilize energy more efficiently, making it easier for them to run uphill.

5. **Conclusion**: Therefore, the answer to the question is that it is much easier for a small animal to run uphill than for a large animal because small animals have a higher metabolic rate.