当不定式、动名词、从句等复杂成分用作宾语且其后跟有宾语补足语时，通常会在宾语补足语前使用形式宾语it，而将真正的宾语移至句末。此时it仍只起先行引导作用，本身无词义。其基本结构为： 动词+it+宾语补足语+不定式（动名词或从句）。
动词+it+that-从句
例如：I take it that he will come.
动词+it+when（if）-从句
例如：I find it difficult to decide when to start the project.
动词+it+介词短语+that-从句
例如：He keeps it in his pocket until the meeting is over.
动词+prep + it + that-从句
例如：See to it that you're not late again.
动词+it+形容词/名词+to do/that从句
例如：I find it necessary to finish the work before tomorrow.
例如：We find it a pleasure to work with you.
动词+it+no use/no good +动名词+其他
例如：He thinks it no use complaining about the situation.
这些句型在高考中也是常考考点，建议同学们多加练习和掌握。