Assertion `:` Contraction of a muscle fibre takes place by the sliding of the thin filaments over the thick filaments.
Reason `:` The central part of thick filament is not overlapped by thin filaments in a resting state.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion .
B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion
C. If Assertion is True but the Reason is False.
D. If both Assertion & Reason are false.

Answer

To solve the question, we need to analyze both the assertion and the reason provided.

### Step 1: Analyze the Assertion
The assertion states: "Contraction of a muscle fibre takes place by the sliding of the thin filaments over the thick filaments."

- This statement is true. Muscle contraction occurs through a mechanism known as the sliding filament theory. In this process, the thin filaments (actin) slide over the thick filaments (myosin), leading to muscle contraction.

### Step 2: Analyze the Reason
The reason states: "The central part of thick filament is not overlapped by thin filaments in a resting state."

- This statement is also true. In a resting muscle fiber, the thin filaments do not overlap the central part of the thick filaments. This area is known as the H zone or H line, which is visible in the sarcomere structure of muscle fibers.

### Step 3: Determine the Relationship
Now we need to determine whether the reason is a correct explanation for the assertion.

- While both statements are true, the reason does not explain how the sliding of the thin filaments over the thick filaments occurs. The mechanism of contraction involves the formation of cross-bridges between actin and myosin, which is not addressed by the reason provided.

### Conclusion
Both the assertion and the reason are true, but the reason is not the correct explanation for the assertion. Therefore, the correct answer is: **Both assertion and reason are true, but the reason is not a correct explanation of the assertion.**

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