If $A = \sin^2 x + \cos^2 x $, then for all real $x$

Question

( A ) $1 \leq A \leq 2$
( B ) $\frac{13}{16} \leq A \leq 1$
( C ) $\frac{3}{4} \leq A \leq 1$
( D ) $\frac{3}{4} \leq A \leq \frac{13}{16}$