答案的确是D Suppose,但是楼上解释不正确.
Suppose在此题中为连词,也可以说成supposing,等于if,意思是“假如/如果”.
即答语中的suppose you finish your homework first
= You can go out and play a game with me (suppose you finish your homework first).
= You can go out and play a game with me (if you finish your homework first).
如果你先做完你作业的话,你就可以出去并和我玩游戏了.