A : If m and `m_(e)` are moving mass, rest mass of a body and c is velocity of light, then kinetic energy of the body is `E=(m-m_(0))c^(2)`
R : Total energy of a body is sum of kinetic energy and rest mass energy.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2).
C. If Assertion is true statement but Reason is false, then mark (3).
D. If both Assertion and Reason are false statements, then mark (4).

Answer

To solve the question, we need to analyze both the assertion (A) and the reason (R) provided.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that the kinetic energy (E) of a body is given by the formula \( E = (m - m_0)c^2 \), where:
- \( m \) is the moving mass (relativistic mass).
- \( m_0 \) is the rest mass of the body.
- \( c \) is the speed of light.
- This formula is derived from the concept of relativistic energy, where the total energy \( E \) of a body in motion is expressed as \( E = mc^2 \).

2. **Understanding the Reason (R)**:
- The reason states that the total energy of a body is the sum of its kinetic energy and rest mass energy.
- Mathematically, this can be expressed as:
\[ E = K + m_0c^2 \]
where \( K \) is the kinetic energy.

3. **Deriving the Kinetic Energy**:
- From the total energy equation, we can rearrange it to find the kinetic energy:
\[ K = E - m_0c^2 \]
- Substituting \( E = mc^2 \) into this equation gives:
\[ K = mc^2 - m_0c^2 \]
- Factoring out \( c^2 \) from the right side:
\[ K = (m - m_0)c^2 \]
- This matches the assertion provided in (A).

4. **Conclusion**:
- Both the assertion (A) and the reason (R) are true.
- Furthermore, the reason (R) correctly explains the assertion (A).

### Final Answer:
- Both A and R are true, and R is the correct explanation of A.