If $ \tan \theta = \large\frac{20}{21}$ then $ \large\frac{1-\sin \theta + \cos \theta}{1+\cos \theta +\sin \theta}$

Question

$\begin{array}{1 1}(A) \; \large\frac{6}{7} \\(B)\;\large\frac{5}{7} \\(C)\;\large\frac{4}{7} \\(D)\; \large\frac{3}{7} \end{array}$