47. They should quit smoking
->They had better quit smoking
48. They once started these machines by hand.
->They used to start these machines by hand
49. He works hard and he will pass the exam
If he works hard, he will pass the exam
50. Ba is a newcomer, and so is Tom
->Both Tom and Ba are newcomer
51. This is the most delicious cake I have ever tasted
I have never tasted a more delicious cake than this
52. She left university 2 years ago.
-> It's 2 years since she left university
53. They had sold the house at the end of the road
The house at the end of the road had been sold
54. It's careless of you to leave the window open last night.
You shouldn't have leave the window open last night.