Well, lets take a look at our options here. Option C is incorrect because PR doesn't equal SQ. D is wrong because it just tells us the same thing, which doesn't help us. A and B are our only answers. B is wrong because we can already see that the angle is a right angle, but we don't know if the hypo is the same, which is needed because without it, we can't tell what the other 2 angles are. A is the right answer.
