The real part of $\begin{vmatrix} \cos \alpha + i \sin \alpha & \cos \beta + i \sin \beta \\ \sin \beta + i \cos \beta & \sin \alpha + i \cos \alpha \end{vmatrix}$ is equal to :

Question

( A ) $2 \sin \beta$
( B ) $2 \cos \alpha$
( C ) 0
( D ) 1