语法题 从每小题所给的A、B、C、D 四个选项中选出可以填入空白处的最佳选项。
Both his parents look sad . Maybe they __what's happened to him .
A. knew B. have known C. must know D.will know
语法题 从每小题所给的A、B、C、D 四个选项中选出可以填入空白处的最佳选项。
Both his parents look sad . Maybe they __what's happened to him .
A. knew B. have known C. must know D.will know
B