With many cities in China dreadfully blanketed by thick haze, the environment problem is _____ Chinese people concern most nowadays.
______ running, learning English needs wills.
_____ man is known by _______ company he keeps.
I was so busy last year that I was almost mad. So I spent _______ I had with my family last month after I finished the project.
After having finished mopping the floor, he puts the mop back ______ it belonged.
The sooner one _____ to the new working conditions, the better it will be _______ his working efficiency.