The state of a continuously mild or partial contraction of a muscle is denoted as

Options

A. tonus
B. tetanus
C. a twitch
D. a reflex contraction

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the state of a muscle that is in a continuously mild or partial contraction.

2. **Identifying the Options**: The options provided are:
- A) Tonus
- B) Tetanus
- C) A twitch
- D) A reflex contraction

3. **Analyzing Each Option**:
- **Option A: Tonus**: This refers to the continuous and passive partial contraction of the muscles, which helps maintain posture and muscle readiness. This is the correct answer.
- **Option B: Tetanus**: This is a sustained muscle contraction that occurs when the motor nerve stimulates the muscle at a high frequency. It is not a mild contraction but rather a strong and sustained one.
- **Option C: A twitch**: A muscle twitch is a quick, involuntary contraction of a muscle fiber or group of fibers. It is not continuous and does not represent a state of mild contraction.
- **Option D: A reflex contraction**: This is a contraction that occurs in response to a stimulus, such as stretching. It is not a continuous state of contraction.

4. **Conclusion**: Based on the analysis, the state of a continuously mild or partial contraction of a muscle is best described by the term "tonus." Therefore, the correct answer is **A) Tonus**.

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