How many non-congruent triangles have vertices at three of the eight points in the array shown below?
[asy]dot((0,0));
dot((0,.5));
dot((.5,0));
dot((.5,.5));
dot((1,0));
dot((1,.5));
dot((1.5,0));
dot((1.5,.5));[/asy]
<spanclass=′latex−bold′>(A)</span> 5<spanclass=′latex−bold′>(B)</span> 6<spanclass=′latex−bold′>(C)</span> 7<spanclass=′latex−bold′>(D)</span> 8<spanclass=′latex−bold′>(E)</span> 9 geometrycongruent triangles