Qingdao will spend about 80,000,000,000 yuan in building a bridge _____ the sea. [ ]

Boys, don’t lose____ in playing Angry Birds. It is bad for your eyes to play computer games for a long time

You should try your best ____ your English.

Jack, ________ put the pens and pencils here and there, please.

I didn’t know when he back. He said he would call me when he home.