Well, if that is wrong I guess you can give the argument that scalene triangle doesn't belong because all the other shapes have equal length sides, and are proportional. They all show symmetry.
You say, look closely, but from the looks of it, you very poorly drew this picture, so how am I supposed to know whether connections are not supposed to be there or if you just fucked up?
your second answer was right titus, (and yes i made that drawing in about 20 seconds, sorry) all the other shapes can be divided in half evenly, the last one can not.