They were lost at sea, _______ the mercy of wind and weather.

Fuzhou Subway Line 1 is under construction,which______to be a big improvement for the local traffic jam.

I am very worried because my son ________ most of his spare time ________ playing games on the computer.

Plants _________carbon dioxide and at the same time _________oxygen. So we may put some in our bedrooms to purify the air. 

— I’m fed up with this rain. How I wish to go hiking this weekend!— Forget it. I’m afraid the wet days will _____.