Cardiac muscles contract

Options

A. quickly and they fatigue
B. rhythmically and are unfatigued
C. slowly and are not fatigued
D. slowly and they fatigue.

Answer

### Step-by-Step Solution:

1. **Understanding Cardiac Muscles**:
- Cardiac muscles are specialized muscles found only in the heart. They are responsible for pumping blood throughout the body.

2. **Characteristics of Cardiac Muscles**:
- Cardiac muscles are involuntary striated muscles. This means that they are not under conscious control (involuntary) and have a striped appearance (striated).

3. **Nature of Contraction**:
- Cardiac muscles exhibit rhythmic contractions. This means that they contract and relax in a regular, repeating pattern, which is essential for maintaining a consistent heartbeat.

4. **Fatigue Resistance**:
- Unlike skeletal muscles, which can become fatigued after prolonged use, cardiac muscles do not fatigue under normal conditions. They continuously contract throughout a person's life without tiring.

5. **Conclusion**:
- Given the characteristics of cardiac muscles, the correct statement is that cardiac muscles contract rhythmically and are unfatigued.

### Final Answer:
Cardiac muscles contract rhythmically and are unfatigued.

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