I don’t know if my father ______back , but I’ll tell you if he ______back.

Figures show that 6 to 10 percent of Internet users become _______ and waste a lot of time.

Do you have any idea why the bus-drivers are on strike? — As far as I know, they are _____ a pay rise.

The problem is difficult students can solve（解答）it.

Last month a new kind of electriccar was produced in Zhengzhou. Its highest _________ can reach 120 kilometresan hour.