b
$\left(A-\frac{I}{2}\right)\left(A^{T}-\frac{I}{2}\right)=I$
$A{A^T} - \frac{{{A^T}}}{2} - \frac{A}{2} = \frac{{3I}}{4}$ .......$(1)$
Similarly $A{A^T} + \frac{{{A^T}}}{2} + \frac{A}{2} = \frac{{3I}}{4}$ ........$(2)$
$(2)-(1) \Rightarrow A+A^{T}=0$
Skew symmetric matrix
But $(1)+(2)$
$\Rightarrow \mathrm{AA}^{\mathrm{T}}=\frac{3 \mathrm{I}}{4}$
But $|A| \neq 0$