If the following system has non-trivial solution,

  px + qy + rz = 0
qx + ry + pz = 0
rx + py + qz = 0 

then which one of the following options is True?

 A p – q + r = 0 or p = q = –r B p + q – r = 0 or p = –q = r C p + q + r = 0 or p = q = r D p – q + r = 0 or p = –q = –r

|A| should be 0 for non-trivial solution.