As the world’s population continues to grow,the ________ of food becomes more and more of a concern. (2013·浙江,4)
It's no _____ arguing about it, because he will never change his mind.
The city was _____ to me, and I didn't know where to go.
The book is not _____ what we paid.
The thief ran away at the _____ of a policeman.
There are usually at least two _____ of looking.