Some countries are increasing their use of natural gas, and other forms of ______. 

The result might not as satisfactory as expected but the ________ on his face told us that he was very happy.

Nowadays more and more people regard traveling as part of their life, and Chinese transport has been strengthened for the holiday travel  ____.

Tom got nothing in______ for her kindness,_____ made him very sad.

Usually a child's behavior is a ________ of his family environment.