Introductory it as Subject
Pattern group 6: it V adj clauseThere are seven patterns in this group, each consisting of it, the verb, an adjective group, and a type of clause. Patterns 6.6 and 6.7 have a prepositional phrase as well.
6.1 it V adj thatIt seems likely that she will leave soon.
6.2 it V adj to-infIt is difficult to see in the dark.
6.3 it V adj whIt became apparent how ill she was.
6.4 it V adj when/ifIt is nice when people compliment you.
6.5 it V adj -ingIt is interesting seeing what happens here.
6.6 it V adj of n to-infIt's nice of you to come.
6.7 it V adj for n to-infIt is impossible for me to arrive any earlier.