1,to do farm work is not easy
变It is not easy to do farm work .
2,to be a scientist is difficult
变Iit is difficult to be a scientist .
3,to write a business letter is not easy
变It is not easy to write a business letter .
4,to find enough time to work is difficult
变It is difficult to find enough time to work .
5,to learn english is very important
变It is very important to learn English .
用指示代词It代替To不定式那一部分句子成分,避免头重脚轻