If $x=\sin^{14}\theta+\cos ^{20}\theta$,then for all $\theta\in R$

Question

$\begin{array}{1 1}(a)\;0< x <1&(b)\;0 < x \leq 1\\(c)\;0 \leq x< 1&(d)\;0 \leq x\leq 1\end{array}$