Viết lại câu thì hiện tại hoàn thành và quá khứ đơn:                                                                                               
55. They have never heard such a thing before.
This is the first time ________________________________________________
56. Noone has challenged his authority before.
This is the first time ________________________________________________
57. She left university 2 years ago
It is _____________________________________________________________
58. My mother was the most warm-hearted person I've ever known.
I have ___________________________________________________________
59. I haven't been able to see them for over a year.
It is _____________________________________________________________
60. It stared to rain at 2 o'clock.
It has ____________________________________________________________
61. I have never been to the ballet before.
It is ______________________________________________________________
62. John and Mary moved to Edinburgh twenty years ago.
It is ______________________________________________________________
63. The police started looking for him two months ago.
For two months now the ______________________________________________
64. I have never seen a dirtier-looking dog.
This is ____________________________________________________________