For a matrix A, AI = A and $AA^{T}=I$ is true when
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → A is a square matrix.
$AI = A \Rightarrow \text{true for all matrices (identity property)}$
$AA^T = I \Rightarrow \text{definition of an orthogonal matrix}$
The condition holds when $A$ is an orthogonal and Square matrix.