一、单项选择。
1、Both his parents look sad . Maybe they _________what happened to him .
Ａ. knew Ｂ. have known Ｃ. must know Ｄ.will know
2、He has _______ been to Shanghai , has he ?
Ａ. already Ｂ.never Ｃ.ever Ｄ. still
3、Have you met Mr Li ______？
Ａ. just Ｂ. ago Ｃ.before Ｄ. a moment ago