4. The number of integer solutions $(m, n)$ for the equation $m^{2}-n^{2}+3 m-7 n-2=0$ is $($.
(A) 1
(B) 2
(C) 3
(D) 4
4.D.

Multiply both sides of the original equation by 4 and complete the square to get
$$
(2 m+3)^{2}-(2 n+7)^{2}=-32 \text {. }
$$

Thus, $(n+m+5)(n-m+2)=2^{3}$.
Since $n+m+5$ and $n-m+2$ have different parities, solving them simultaneously yields
$$
(m, n)=(-5,1),(2,1),(2,-8),(-5,-8) .
$$