单项选择题
You look（） What（）you（）
A.tire；did；do B.tiring；have；done C.tired；do；do D.tired；have；been doing
单项选择题 You must explain（）how they succeeded（）the experiment.
单项选择题 We（）every day when we were children.
单项选择题 We must make a difference between（）language and（）language.
