Science and technology have in important ways contributed to the improvement of agricultural production. 

(2013·哈尔滨四校高三统一检测)In fact fuels we burn and plant food we eat ________ their chemical energy in the form of heat.

When he heard that his job application had been rejected, he struggled to _______ his feelings. 

_______ is known to the world, the Chinese in many places _______ the old traditions.

I ___ read your letter when the bell rang.