."It is＋形容词＋of sb.to do sth.."和"It is＋形容词＋for sb.to do sth.."这两个句型使用频率都很高.前者表示说话人对客观事物的高兴、惊讶、遗憾、难过等情绪,表现的是人的性格、品质或特征,经常可以转换成：①How＋形容词＋it is＋of sb.to do sth.!②How＋形容词＋of sb.to do sth.!③Sb.＋is＋形容词＋to do sth..或④That is＋形容词＋of sb.to do sth.等；后者表示说话人对客观事件的决断性,根据具体情况可以转换成：①To do sth.is＋形容词；②It is＋形容词＋that从句.如：
It is possible to work out whether you will save or lose money by increasing the temperatureby1℃.(利用计算机)能够计算出温室里的温度升高一度会使你赚钱还是赔钱.
Is it necessary to complete the design before National Day?在国庆节前完成这一设计有必要吗?
It is stupid of him to refuse the invitation.他拒绝了邀请,真是件错事.
上一句可转换成：How stupid it is of him to refuse the invitation!
或How stupid of him to refuse the invitation!
或He is stupid to refuse the invitation.
It is better for you to live alone for sometime.你单独住一段时间更好.
上一句可转换成：To live alone for sometime is better.
或It is better that you live alone for sometime.