31. It's the most beautiful building I have ever seen. 
This is the first time I have seen such a beautiful building.
32. I have taught English for 15 years. 
33. The last time she played football was over three years. 
She last played football over three years ago. 
It's over three years since she last played football. 
34. It's (high) time he got back to work. 
35. Not until I got home did I forget about the gun. 
36. Hardly had I just put the phone down when the boss rang back. 
No sooner had I just put the phone down than the boss rang back. 
37. The child apologised for breaking the the flower vase. 
38. The rough sea prevented us from swimming. 
The rough sea made it difficult for us to swim. 
39. There is no point in asking him for money. 
40. While we were discussing, he came in.