As the world’s population continues to grow,the ________ of food becomes more and more of a concern. (2013·浙江,4)
It takes a lot of______ to become a good swimmer.
After three months, these young students finally became used to the ______ of life in a big city abroad.
Although the working mother is very busy, she still_____ a lot of time to her children.
Honesty is the most important______ a man can have.
Probability is the mathematical study of the _____ of an event's occurrence.