Introductory it as Subject
Pattern group 5: it V n clauseThere are eleven patterns in this group, each consisting of it, the verb, a noun group, and a type of clause. Patterns 5.8 to 5.11 contain other elements as well.
5.1 it V n thatIt struck me that the story would make a good film.
5.2 it V n to-infIt worries me to see you unhappy.
5.3 it V n whIt beats me why sales are falling.
5.4 it V n when/ifIt worries me when you come home late.
5.5 it V n -ingIt's no fun working all weekend.
5.6 it V n/amount before/sinceIt's only a matter of time before he finds out.
5.7 it V n for n to-infIt took months for them to answer my letters.
5.8 it V n n to-infIt took me ages to finish my work.
5.9 it V amount for n thatIt said a lot for him that he was able to apologize.
5.10 it V n adj thatIt drove him crazy that he couldn't do anything to help.
5.11 it V n adj to-infIt makes me sick to think about all the thefts.