单句语法填空
1．The doctor advised my father ____________(stop) smoking; it was harmful to his health.
答案：to stop
2．They were heard ____________(sing) a song.
答案：to sing
3．We saw the pupils ____________(sweep) the floor we passed by.
答案：sweeping
4．He is the only one of the students who ____________(elect)．
答案：was elected
5．A large number of students in our class ____________(be) girls.
答案：are
