Which of the following muscles act involuntarily? (a) Striated muscles (b) Smooth muscles © Cardiac muscles (d) Skeletal muscles

Options

A. (a) and (b)
B. (b) and (c)
C. (c) and (d)
D. (a) and (d)

Explanation

To determine which muscles act involuntarily from the given options, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Types of Muscles**:
- The question provides four types of muscles: Striated muscles, Smooth muscles, Cardiac muscles, and Skeletal muscles.

2. **Understand Muscle Classification**:
- **Striated Muscles**: Also known as skeletal muscles, these are voluntary muscles that we can control consciously (e.g., moving arms and legs).
- **Smooth Muscles**: These are unstriated muscles and are involuntary. They function without conscious control (e.g., movements in the digestive tract).
- **Cardiac Muscles**: Found only in the heart, these muscles are also involuntary and cannot be controlled consciously.

3. **Analyze Each Option**:
- (a) Striated muscles: Voluntary (not involuntary)
- (b) Smooth muscles: Involuntary (correct)
- (c) Cardiac muscles: Involuntary (correct)
- (d) Skeletal muscles: Voluntary (not involuntary)

4. **Select the Correct Options**:
- The muscles that act involuntarily are Smooth muscles (b) and Cardiac muscles (c).

5. **Conclusion**:
- Therefore, the correct answer is (b) Smooth muscles and (c) Cardiac muscles.

### Final Answer:
The muscles that act involuntarily are **(b) Smooth muscles and (c) Cardiac muscles**.

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