B. In the Cartesian coordinate system, there are points $A(-1,2)$, $B(3,2)$. If $C$ is a point on the coordinate axes, and $\triangle ABC$ is a right triangle, then the number of points $C$ that satisfy the condition is ( ) .
(A) 3
(B) 4
(C) 5
(D) 6
B. C.

In $\triangle A B C$, if $\angle A$ or $\angle B$ is a right angle, then point $C(-1,0)$ or $C(3,0)$; if $\angle C$ is a right angle, then point $C$ is the point where the circle with $A B$ as its diameter is tangent to the $x$-axis, or one of the two intersection points with the $y$-axis. Therefore, there are 5 points $C$ that satisfy the conditions.