3. The monotonic increasing interval of the function $\log _{\frac{1}{4}}\left(x^{2}-2 x-3\right)$ is
A. $(-\infty, -1)$
B. $(-\infty, 1)$
C. $(1, +\infty)$
D. $(3, +\infty)$
3. A Prompt: The monotonically increasing interval of the function $\log _{\frac{1}{2}}\left(x^{2}-2 x-3\right)$ is the monotonically decreasing interval of $f(x)=x^{2}-2 x-3$, and the value is greater than 0.