题目

 Would you mind ________ the window, please? It’s so cold.        A to close           B close                C closing 答案：C;  A=2x2-3xy+2y2，B=2x2+xy-3y2，那么B-A等于A.2xy-5y2B.4xy+5y2C.-2xy-5y2D.4xy-5y2