Subject :IMO Class : Class 9

If the roots of (p - q)

^{2}x^{2}+ 2 (p^{2}- q^{2}) x + k = 0 are equal, then k = ________.(A) (p + q)^{2 }

(B) (p - q)^{2}

(C) p^{2} - q^{2}

(D) 0