question_answer

If the lines \[(p-q){{x}^{2}}+2(p+q)xy+(q-p){{y}^{2}}=0\] are mutually perpendicular, then          

A)            \[p=q\]                                   

B)            \[q=0\]                                   

C)            \[p=0\]                                   

D)            p and q may have any value