If c is the vertex and AB is the bottom, c must be on the perpendicular of AB. According to the meaning of the question, c (0,0).

Draw a circle with A as the vertex and AB as the radius, and there are three intersections with the coordinate axis that are different from B and the origin.

Draw a circle with B as the vertex and AB as the radius, and there are three intersections with the coordinate axis that are different from A and the origin.

It adds up to seven.

Choose C.