Mr. Wang decided to devote all his time_______ his spoken English before going abroad.

We firmly believe that war never settles anything．It only       violence．

With the development of science and technology, the prices of TV sets have ________.

 Last week the students did the experiment in order to_______ if iron rusts in dry air．

Some children are too selfish today. They should be taught to _____things with others so that they will show concern for others.