What is the relation between p and q, such that the roots of the equation p/(x-p) + q/(x-q) = r, are equal but opposite in sign? p,q and r are constants.

a. pq = 0,
b.) pq = -1
c.) p+ q =0
d.) p+ q = pq
e.) p+ q = -1

Any particular approach to solve such questions?