从A、B、C、D四个选项中，选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。
21．---- May I use your new dictionary? I want to look a word up．
---- It’s over there．_______ ．
A．No problem B．Got it C．Feel free D．It depends
22．As is often ______ case, watching films in English can be both ______ fun and useful for language learning．
A．the; a B．the; / C．a; / D．a; a
23．The relationship between parents and children is of ______ importance．
A．vital B．powerful C．typical D．good
