4. The real number $b$ satisfies $|b|<3$, and there exists a real number $a$, such that $a<b$ always holds. Then the range of values for $a$ is ( ).
(A) $(-\infty, 3]$
(B) $(-\infty, 3)$
(C) $(-\infty,-3]$
(D) $(-\infty,-3)$
4. C.

From $|b|<3 \Rightarrow -3<b<3$.
Since $a<b$ always holds, hence $a \leqslant -3$.