Assertion: The planet move slower when they are farther from the Sun than when they are nearer.
Reason : Angular velocity of a planet is a constant quantity.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion
B. If both assertion and reason are truebut 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

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

**Assertion:** The planets move slower when they are farther from the Sun than when they are nearer.

**Reason:** The angular velocity of a planet is a constant quantity.

### Step-by-Step Solution:

1. **Understanding Kepler's Laws:**
- According to Kepler's Second Law (Law of Areas), a line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time. This means that the areal velocity (area swept out per unit time) is constant for a planet orbiting the Sun.

2. **Implications of Kepler's Second Law:**
- Since the areal velocity is constant, when a planet is closer to the Sun, it must move faster to sweep out the same area in the same amount of time. Conversely, when a planet is farther from the Sun, it moves slower.

3. **Analyzing the Assertion:**
- The assertion states that planets move slower when they are farther from the Sun. This is consistent with Kepler's Second Law, which confirms that the assertion is true.

4. **Analyzing the Reason:**
- The reason states that the angular velocity of a planet is a constant quantity. However, this is not correct. The angular velocity (which is the rate of change of the angle with respect to time) is not constant for planets in elliptical orbits. It varies depending on the distance from the Sun. Therefore, the reason is false.

5. **Conclusion:**
- Since the assertion is true and the reason is false, the correct answer is that the assertion is true, but the reason is false.

### Final Answer:
The assertion is true, but the reason is false.

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