If $\tan \theta = \large\frac{20}{21}$, then the value of $\large\frac{1- \sin \theta + \cos \theta }{1+ \sin \theta + \cos \theta }$ is _______

Question

$\begin{array}{1 1}(A) \; \large\frac{3}{5} \\(B)\;\large\frac{3}{7} \\(C)\;\large\frac{3}{4} \\(D)\;\large\frac{3}{8} \end{array}$