21. —Did you have _____ fun in Australia?
—Sure. It was _____ unforgettable experience.
A. a; an B. /; the C. the; an D. /; an
22. We could see nothing in the thick fog at a _____ of two meters, so we got lost.
A. length B. distance C. space D. way
23. —What do you think of the good news?
—Wonderful! It makes us _____．Most of us were _____about it
