A. I can't say so B. I expect so C. I'm sure so D. I don't know so
单项选择题Do you hear someone knocking at the door Yes, I did. I heard him () three times.
A. knocking B. knocked C. being knocking D. knock
单项选择题You can take()seat you like.
A. no matter what B. no matter which C. what D. whichever