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’ll get early start tomorrow.
A．/; the B．a; an C．/; an D．the; an
22. Have you ever dreamt of _______a chance for you to be sent abroad for a visit ?
A. it being B. there being C. there is D. to be
23. I reflected _____ possible reasons whether I would go.
A. for B. with C. of D. on
