Assertion `:` When a girl sitting on a swing stands up, the periodic time of the swing will increase.
Reason `:` In standing position of the girl, the length of swing will increase.

Options

A. Statement-1 is True, Statement-2 is True , Statement-2 is a corrrect explanation for Statement-1
B. Statement-1 is True, Statement-2 is True , Statement-2 is NOT a corrrect explanation for Statement-1
C. Statement-1 is True, Statement-2 is False.
D. Statement-1 is False, Statement-2 is False.

Answer

To solve the question regarding the assertion and reason provided, we will analyze both statements step by step.

### Step 1: Understanding the Assertion
The assertion states that "When a girl sitting on a swing stands up, the periodic time of the swing will increase."

**Analysis**:
- The periodic time (T) of a swing (or a pendulum) is given by the formula:
\[ T = 2\pi \sqrt{\frac{L}{g}} \]
where \(L\) is the length of the pendulum and \(g\) is the acceleration due to gravity.
- If the girl is sitting, the center of mass of the system (girl + swing) is lower compared to when she stands up.

### Step 2: Understanding the Reason
The reason states that "In the standing position of the girl, the length of the swing will increase."

**Analysis**:
- When the girl stands up, her center of mass rises, effectively reducing the length of the pendulum (swing) from the pivot point to her center of mass.
- Thus, the effective length \(L\) of the swing actually decreases when she stands up.

### Step 3: Conclusion
- Since the effective length \(L\) decreases when the girl stands up, the periodic time \(T\) will also decrease (because \(T\) is proportional to the square root of \(L\)).
- Therefore, the assertion is incorrect (the periodic time does not increase) and the reason is also incorrect (the length does not increase).

### Final Answer
Both the assertion and the reason are false.