Only when _____ be possible to sign the contract.

_____ from endless homework on weekends, the students now find their own activities, such as taking a ride together to watch the sunrise[ ]

(2014·郑州一检)—Who is late for class again?—________you ask？Tim，of course.

The opening ceremony has been put off_____ the bad weather

Among the 15-year-old children, some ____ studying in university while others are still learning to read and write.