56._________A. prospectiveB. coming C. existingD.

___________! There’s a train coming. A. Look out B. Look around C. Look forward

—May I open the window to let in some fresh air ？—___________A. Come on B. Take care C.

56._________A. refersB. concernsC. turnsD. comes

_________(56)A.came B.comingC.comes D.come

56._________A.refers B.concerns C.turns D.comes

Before the guests come I must get the glasses ______.A. washed B. to be washed C. bei