Students in our school are encouraged to________more activities after class in order to broaden their knowledge.[ ]

Mr. Wei wants ________to Beijing.

He didn’t attend the meeting last night, _________ he doesn’t know our plan for the picnic.

He is a key ____________ in the murder so we must protect him from all kinds of danger

Now the air in Yancheng is _______ than it used to be . We should do something to stop it .