Which of the following is true for $A=\left[\begin{array}{cc}1 & -1 \\ 2 & 3\end{array}\right]$?

A + 4I is symmetric, where I is an Identity matrix of order 2 A - 4I is skew symmetric, where I is an Identity matrix of order 2 A - B is a diagonal matrix for any value of $\alpha$ if $B=\left[\begin{array}{cc}\alpha & -1 \\ 2 & 5\end{array}\right]$ $AA^{T}$ is a skew symmetric matrix.

A - B is a diagonal matrix for any value of $\alpha$ if $B=\left[\begin{array}{cc}\alpha & -1 \\ 2 & 5\end{array}\right]$

The correct answer is Option (3) → A - B is a diagonal matrix for any value of $\alpha$ if $B=\left[\begin{array}{cc}\alpha & -1 \\ 2 & 5\end{array}\right]$