Assertion : The up and down movements of four arms are controlled by two types of muscles, biceps and triceps.
Reason : Biceps : Biceps are the muscles that straighten the arm and triceps are the muscles that bend the arm.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Assertion**: The assertion states that the up and down movements of the forearms are controlled by two types of muscles: biceps and triceps. This statement is true because these muscles are indeed responsible for the movement of the forearm.

2. **Understanding the Reason**: The reason provided states that biceps are the muscles that straighten the arm and triceps are the muscles that bend the arm. This statement is incorrect. In fact, biceps are the muscles that bend the arm (flex the elbow), while triceps are the muscles that straighten the arm (extend the elbow).

3. **Analyzing the Relationship**: Since the assertion is true and the reason is false, we need to determine which option correctly describes this relationship.

4. **Evaluating the Options**:
- Option 1 states that both assertion and reason are true and that the reason is a correct explanation of the assertion. This is incorrect.
- Option 2 states that both assertion and reason are true, but the reason is not the correct explanation of the assertion. This is also incorrect.
- Option 3 states that the assertion is true but the reason is false. This is correct.
- Option 4 states that both assertion and reason are false. This is incorrect.

5. **Conclusion**: The correct answer is option 3: assertion is true but reason is false.