16. It must be _______ great fun to go camping on a mountaintop with your best friends.
A. a B. the C. / D. an
17. I was able at last to _______ my mother out of buying the red dress.
A. suggest B. advise C. persuade D. command
18. It was because of bad weather _______ the sports meeting had to be put off.
A. so B. how C. why D. that
