1. Let $x \in\left(-\frac{1}{2}, 0\right)$, the size relationship of the following three numbers $a=\cos (\sin x \pi), b=\sin (\cos x \pi), c=$ $\cos (x+1) \pi$ is ( ).
A. $c<b<a$
B. $a<c<b$
C. $c<a<b$
D. $b<c<a$
1. A.

Let $y = -x$, then $y \in \left(0, \frac{1}{2}\right)$, and $a = \cos (\sin y \pi)$, $b = \sin (\cos y \pi)$, $C = \cos (1 - y) \pi$. Given $0 < b < a$.