Find all possible values of $p$ and $q$ for which $\cos^{-1}\sqrt p+\cos^{-1}\sqrt{1-p}=\large\frac{3\pi}{4}$

Question

$\begin{array}{1 1}(a)\;p=0,q=\large\frac{1}{2}&(b)\;p \leq 2,q=1\\(c)\;0 \leq p\leq 1,q=\large\frac{1}{2}&(d)\;None\;of\;these\end{array}$