36.　　　 (necessary, impossible, ….)

35.　　　 It is important that we (should) learn it well.

34.　　　 It was in the town that I was born.

33.　　　 It is the town where I was born.

32.　　　 It is (high)time (that) he went to school

31.　　　 It was the first time(that) I had visited the place.

30.　　　 It is the first time(that) I have been here.

29.　　　 It was a long time since I had met you last.

28.　　　 It has been a long time since I met you last.

27.　　　 It is a long time since I met you last.