If A is a square matrix such that `A-A^(T)=0`, then which one of the following is correct ?

Options

A. A must be a null matrix
B. A must be a unit matrix
C. A must be a scalar matrix
D. none of the above

Answer

To solve the problem, we need to analyze the given condition for the square matrix \( A \).

### Step-by-Step Solution:

1. **Understand the Given Condition**:
We are given that \( A - A^T = 0 \). This implies that \( A = A^T \).

2. **Interpret the Result**:
The equation \( A = A^T \) indicates that the matrix \( A \) is equal to its transpose. This is the definition of a symmetric matrix.

3. **Conclusion**:
Since \( A \) is equal to its transpose, we conclude that \( A \) is a symmetric matrix. Therefore, the correct option is that \( A \) is a symmetric matrix.