In spite of his disappointment, he _______ a weak smile. 

—Jimmy, had a lot of parties recently.—Yes, that might _____ his failure in the examination.

 It is high time that we started to consider what ________  we should take to reduce heavy smog caused by traffic fumes and other pollutions.

Peter’s jacket looked just the same as Jack’s，but it cost______his.

--Dan’s talking about getting a cat from one of his relatives.--Yeah. I hear his apartment building is about to ________ the ban on pets.