H-zones are found in

Options

A. myofibril of unstriated muscle
B. myofibril of striated muscle
C. light band
D. none of the above

Answer

### Step-by-Step Solution:

1. **Understanding H-Zone**: The H-zone is a specific region found within the sarcomere of striated muscle fibers. It is important to know that the H-zone is located in the center of the sarcomere.

2. **Composition of H-Zone**: The H-zone is characterized by the presence of thick filaments, specifically myosin, and it does not contain any thin filaments (actin). This is crucial because it differentiates the H-zone from other areas in the sarcomere.

3. **Relation to Sarcomere Structure**: The sarcomere is the basic contractile unit of striated muscle. It consists of various bands and zones:
- The A-band contains both thick (myosin) and thin (actin) filaments.
- The I-band contains only thin filaments (actin).
- The H-zone is a subdivision of the A-band where only thick filaments are present.

4. **Behavior During Muscle Contraction**: During muscle contraction, the H-zone shrinks as the actin filaments slide over the myosin filaments, which is an important aspect of muscle physiology.

5. **Conclusion**: Given the options provided in the question, the H-zone is found in the myofibril of striated muscle. Therefore, the correct answer is **myofibril of striated muscle**.

### Final Answer:
The H-zones are found in **myofibril of striated muscle**.

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