It is estimated the project will last four years.

　　據估計，這項工程將持續四年。

　　The child disappeared from his home some time after four.

　　這孩子四點(diǎn)多的時(shí)候就離家不見(jiàn)了。

　　She asked her students to get into groups of four.

　　她讓學(xué)生每四人分為一小組。

　　First get students to form groups of four.

　　首先讓學(xué)生分成四人一組。

　　Students come here from the four corners of the world.

　　學(xué)生從世界各地來(lái)到這里。