The expressionP−QP+Q−P+QP−Qwhere P=x+y and Q=x−y, is equivalent to:<spanclass=′latex−bold′>(A)</span>xyx2−y2<spanclass=′latex−bold′>(B)</span>2xyx2−y2<spanclass=′latex−bold′>(C)</span>1<spanclass=′latex−bold′>(D)</span>xyx2+y2<spanclass=′latex−bold′>(E)</span>2xyx2+y2