If A and B are square matrices of the same order then

If $A$ and $B$ are square matrices of the same order then $(A+B)^{2}=$ ?

A. $A^{2}+2 A B+B^{2}$

B. $A^{2}+A B+B A+B^{2}$

$C \cdot A^{2}+2 B A+B^{2}$

D. none of these