We _________be too careful while dealing with these social problems.

— I have got a headache. — No wonder. You _____in front of that computer too long.[ ]

Heavy smog blankets Beijing．,city authorities start using its new smog warning system

My brother knows little Japanese, ______ he can’t understand the instructions of his camera.

The young man lay on the sofa with his arms ________ andsoon fell asleep．