33. Because of the current economic depression, days are gone when 5-star hotels in Shanghai ______ charge 6,0000 youn for one night.

.You should remember the cause and avoid it the next time you __________ the same situation.

Seeing their teacher _______ into the classroom, they stopped _______ at once.

were two boys in the lab, _______ did theexperiment successfully.

_______, I believe, and you will find the student is very outgoing.