Once we discover a mistake, we should not _____ it but correct it immediately, to create better conditions for economic development.

(2013·烟台高三二模)It was a difficult job for him.He had tried everything but it made little ________.

In order to reduce   air pollution, many people want  a total _____on the playing of firecrackers (鞭炮)in many cities during the Spring Festival.

 There are 5 star fathers in the TV program Dad, Where are we going, the Olympic Champion Tian liang ________. 

(2013·哈尔滨四校高三一模)In fact fuels we burn and plant food we eat ________ their chemical energy in the form of heat.