21. As we all know, _______ mankind has realized the walk in ______ space.
A. the; the B. /; the C. /; / D. the; /
22. Some students, hoping to get a high score, are _______ about the results of coming exam.
A. absurd B. guilty C. anxious D. puzzling
23. All cases ______ children are dealt with in a special children’s court.
A. concerned B. concerning C. concern D. to concern
