Don’t smoke in the classroom, （）.

单项选择题Skating is such a （） sport in the northeast of China that almost everybody there knows how to skate.

A. likely
B. famous
C. popular
D. long

单项选择题He did not go to school yesterday because he （） his father who was ill.

A. must have looked after
B. would have to look after
C. had to look after
D. should have looked after