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． — Oh, must you? Stay a bit longer. It has been such ________ fun having you.
— Thanks. Anyway, I’ve got ________ early start tomorrow morning.
A. a; an B. / ; an C./ ; the D. the; an
22． My daughter doesn’t know what to ________ at the university; she can’t make up her mind about her future.
A. take on B. take away C. take up D. take after
23． Although this ________ sound like a simple task, great care is needed.
A. must B. shall C. may D. should
