16. -It was_______ great fun to be a host, wasn't it?
- Yes. It was_______ experience hard to forget.
A. /;an B. a; an C. ;the D. a; the
17. The Internet has helped to change our life in many ways_______ the past 20 years.
A. after B. with C. among D. over
18. Look! The trail walkers are walking with_______ bodies. The walk must be very_______.
A. tired; tired B. tired; tiring C. tiring; tired D. tiring; tiring
19. The teacher was very grateful_______ you did.
A. to what B. to that C. for what D. for that
20. -Where is your father?