$z=\large\frac{1}{1-\cos \theta+i\sin \theta}$.Re(z) is equal to

Question

$\begin{array}{1 1}(A)\large\frac{1}{1-\cos \theta} \\ (B) 1- \cos \theta \\ (C) \large\frac{1}{2} \\(D) 2 \end{array}$