Correct Answer: C only

Everything makes sense to me except to rule B out. If one angle of a parallelogram is 90°, then it’s opposite must be 90° right? Then the other two have to add up to 180° and be the same so they, too would each be 90°? 2 sets of parallel lines, 4 angles that are each 90° and this parallelogram also sounds like a square.

I can’t think of what a parallelogram with only one 90° would look like.