—You look unhappy, my son?—I’m wondering how long it’ll be we come to China again.
___ smoking here will be fined.
_____ with a good education can apply for the job.
According to the rules, students must not _____ their books during examinations.
She may have missed the train, in _____ case she won't arrive for another hour.
He had a lot of friends, none of _____ could lend him any money.