Anticipatory it
it用來(lái)充當(dāng)形式主語(yǔ)或形式賓語(yǔ),后面的真正主語(yǔ)或真正賓語(yǔ)通常是不定式結(jié)構(gòu)、動(dòng)名詞或名詞性分句。It的這種用法叫作先行it。
eg.
It is quite important for us to form a good studying habit.
I think it important to finish the task in time.
it用來(lái)充當(dāng)形式主語(yǔ),后置的真正主語(yǔ)往往可以取代先行it的位置,出現(xiàn)在句首。