21. You must be aware ______the fact that it is ____ great importance to learn English well.
A. to; of B. of; of C. to; in D. of; in
22. –What has happened to Jack?
–He’s had one of his legs _____trying to save a boy from the fire.
A. injuring B. injured C. being injured D. to be injured
23. –How was your trip abroad?
–Great. The only pity is that I ______to buy some gifts for my friends.
A. forgot B. forget C. would forget D. was forgetting
