16." Don't forget to bring along the raincoat" Thuy's grandma said
Thuy's grandma reminded..........her to bring along the raincoat...
17. The last time Thuy met her old friends was when they left school
Thuy hasn't.......met her old friends since they left school ....
18.They will have to change the date of the meeting again
The date...... of the meeting will have to be changed again 
19.I don't have a key, so I can't get in
If..........you had a key, i could get in
20.I'm too poor to take a space trip
I'm not........rich enough to take a space trip