原型为 To finish the thesis took me a month. 用 it 作形式主语替代不等式 to finish the thesis。
原型为 Making another try is worthwhile. 用 it 作形式主语替代动名词 making.
用 it 作形式主语替代由 that 引导的名词性从句 She was not at home when I called
4. 用于强调句，去掉 “ it is … that … ”，剩余部分仍能组成一完整句子。
练习. He made many mistakes in his composition because of ________ .
|A. careless||B. careful||C. carelessness||D. carefulness|