Assertion: Kepler's second law can be understood by conservation of angular momentum principle.
Reason: Kepler's second law is related with areal velocity which can further be proved to be used on coservation of angular momentum as `(dA//dt)=(r^(2)omega)//2`.

Options

A. Statement I is True, Statement II is True: Statement II is a correct explanation for Statement I.
B. Statement I is True, Statement II is True: Statement II is Not a correct explanation for Statement I.
C. Statement I is True, Statement II is False.
D. Statement I is False, Statement II is True.

Explanation

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

**Assertion:** Kepler's second law can be understood by the conservation of angular momentum principle.

**Reason:** Kepler's second law is related to areal velocity, which can further be proved to be used on conservation of angular momentum as \( \frac{dA}{dt} = \frac{r^2 \omega}{2} \).

### Step-by-Step Solution:

1. **Understanding Kepler's Second Law:**
- Kepler's second law, also known as the law of areas, states that a line segment joining a planet to the Sun sweeps out equal areas during equal intervals of time. This implies that the areal velocity (area swept per unit time) is constant.

2. **Areal Velocity:**
- The areal velocity \( \frac{dA}{dt} \) can be expressed in terms of the radius \( r \) and the angular velocity \( \omega \). The area \( A \) swept out by the radius vector in a small time interval \( dt \) can be approximated as:
\[ dA = \frac{1}{2} r^2 d\theta \]
- Therefore, the areal velocity is given by:
\[ \frac{dA}{dt} = \frac{1}{2} r^2 \frac{d\theta}{dt} = \frac{1}{2} r^2 \omega \]

3. **Conservation of Angular Momentum:**
- Angular momentum \( L \) for a planet moving in an orbit is given by:
\[ L = mvr = m r^2 \omega \]
- Since there are no external torques acting on the planet, the angular momentum is conserved:
\[ L = \text{constant} \]
- This means that \( m r^2 \omega \) remains constant, which implies that the product \( r^2 \omega \) is also constant for a given mass \( m \).

4. **Connecting Kepler's Second Law and Angular Momentum:**
- From the expression for areal velocity, we see that:
\[ \frac{dA}{dt} = \frac{1}{2} r^2 \omega \]
- Since \( r^2 \omega \) is constant (due to conservation of angular momentum), it follows that \( \frac{dA}{dt} \) is also constant. This directly supports Kepler's second law.

5. **Conclusion:**
- Both the assertion and reason are true. The assertion that Kepler's second law can be understood through the conservation of angular momentum is valid, and the reason provides a correct explanation of this relationship.

### Final Answer:
Thus, the answer is that both statements are true, and the reason is the correct explanation of the assertion.