3. Let $\angle A, \angle B, \angle C$ be the three interior angles of $\triangle ABC$. Proposition $P: \angle A=\angle B$;
Proposition $Q: \sin \angle A=\sin \angle B$.
Then $\neg P$ is $\neg Q$'s ( ) condition.
(A) sufficient but not necessary
(B) necessary but not sufficient
(C) sufficient and necessary
(D) neither sufficient nor necessary
3. C.

In $\triangle A B C$,
$$
\angle A \neq \angle B \Leftrightarrow \sin A \neq \sin B .
$$