Read the following statements (A to D) and select the one option that contains both correct statements.
A. Z-line is present in the centre of the light band.
B. Thin filaments are firmly attached to the M-line.
C. The central part of thick filaments, not overlapped by thin filaments is called Z-band.
D. Light band contains only thin filaments.

Options

A. (1) A and D
B. (2) B and C
C. (3) A and C
D. (4) B and D

Answer

To solve the question, we need to evaluate each of the statements (A to D) regarding the structure of the sarcomere and determine which two statements are correct.

**Step 1: Analyze Statement A**
- Statement A claims that the Z-line is present in the center of the light band.
- The light band, also known as the I band, is indeed where the Z-line is located at its center. This statement is **correct**.

**Step 2: Analyze Statement B**
- Statement B states that thin filaments are firmly attached to the M-line.
- In reality, thin filaments (actin) are attached to the Z-line, while the M-line is the center of the thick filaments (myosin). This statement is **incorrect**.

**Step 3: Analyze Statement C**
- Statement C says that the central part of thick filaments, not overlapped by thin filaments, is called the Z-band.
- This is incorrect as the central part of thick filaments that is not overlapped by thin filaments is referred to as the H zone, not the Z-band. Therefore, this statement is **incorrect**.

**Step 4: Analyze Statement D**
- Statement D claims that the light band contains only thin filaments.
- This statement is correct because the I band (light band) is composed solely of thin filaments (actin). This statement is **correct**.

**Conclusion:**
The correct statements are A and D. Therefore, the option that contains both correct statements is the one that includes A and D.

**Final Answer:**
The option that contains both correct statements is **A and D**.

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