7. Place three consecutive positive integers $a, b, c$ in any order (different orders are considered different groups) into
$$
\square x^{2}+\square x+\square=0
$$

as the quadratic coefficient, linear coefficient, and constant term of a quadratic equation. The number of groups of $a, b, c$ that make the resulting equation have at least one integer root is ( ).
(A) does not exist
(B) there is one group
(C) there are two groups
(D) more than two groups
7.C.

Let the three consecutive positive integers be $n-1, n, n+1$ (where $n$ is an integer greater than 1). When the coefficient of the linear term is $n-1$ or $n$, $\Delta$ is less than zero, and the equation has no real roots; when the coefficient of the linear term is $n+1$, $\Delta=(n+1)^{2}-4 n(n-1)=-3(n-1)^{2}+4$.
Since $n$ is an integer greater than 1, to make $\Delta \geqslant 0$, $n$ can only be 2.

When $n=2$, the equations $x^{2}+3 x+2=0, 2 x^{2}+3 x+1=0$ both have integer roots, so the only pairs $(a, b, c)$ that satisfy the requirements are $(1,3,2)$ and $(2,3,1)$.