4. For a real number $x$, the symbol $[x]$ represents the greatest integer not greater than $x$, for example, $[3.14]=3,[-7.59]=$ -8. Then the number of integer solutions for the equation $\left[\frac{3 x+7}{7}\right]=4$ is ( ).
(A) 4
(B) 3
(C) 2
(D) 1
4.B.

From $\left[\frac{3 x+7}{7}\right]=4$, we know $4 \leqslant \frac{3 x+7}{7}<5$, which gives $7 \leqslant$ $x<\frac{28}{3}$. Therefore, $x=7,8,9$.