If $A=[a_{ij}]$ be a square matrix of order n, then the correct statements are :

A. A is a symmetric matrix if and only if $A^T=A$

B. A is a skew-symmetric matrix if and only if $A^T=-A.$

C. If order of A is $n×n$, then order of $A^T$ is $m×n (m ≠n).$

D. If $\begin{bmatrix} 1 & 2 \\3 & 4\end{bmatrix}=\begin{bmatrix}1 & 2\\3 & 2x\end{bmatrix}, $ then $x=4 $.

Choose the correct answer from the options given below:

A, B only