1. Given
$$
f(x)=\left\{\begin{array}{ll}
\left(\frac{1}{4}\right)^{x}, & x \in(-\infty, 1) ; \\
\log _{\frac{1}{2}} x, & x \in[1,+\infty) .
\end{array}\right.
$$

Then $f(f(-1))=()$.
(A) 2
(B) -2
(C) $\frac{1}{4}$
(D) $-\frac{1}{2}$
$$
-1 . B \text {. }
$$

From the problem, we know that
$$
f(f(-1))=f(4)=\log _{\frac{1}{2}} 4=-2 \text {. }
$$