51. Simon is helpful, he often ____________(提供) me help .
52. Susan is an __ ______(极好的) friend. We all like her.
53. No one knows (确切地) when Chinese first grew watermelons.
54. Tom is one of the best ______________(游泳者)in our class.
55. You should look （自始至终）the instructions first.
56. I’m sure he can finish the work in time by . (he)
57. We are (certain) what will happen. Let’s wait and see.
58. Your diet seems to work very well. You look much (slim) now.
59. The teacher made the students ____________(discuss) with each other in class.
60. The ticket is _____________(use) now, however, I’ll keep it.