6/ A
7/ A
8/ A
9/ A
10/B
11/ A
12/ A
13/ A
14/C
15/ A
16/ She became extremely successful since she has been in Switzerland.
-> has been -> was
17. For Ronnie began classes, he has met an average of 1.324 people a month.-> For -. since
18. Petrol is twice as expensive as it is a few years ago.-> is-> was
19. Please contact me with the above -> with -> on
GOOD LUCK !