Editor
In a triangle OPQ, if $Q=90^{\circ} and OP is hypotenuse, then:
Difficulty: Hard
A: 
$(OP)^{2}=(PQ)^{2}-(OQ)^{2}$
B: 
$(OQ)^{2}=(OP)^{2}-(PQ)^{2}$
C: 
$(PQ)^{2}=(OP)^{2}+(OQ)^{2}$
D: 
$(OQ)^{2}=(PQ)^{2}-(OP)^{2}$