请认真阅读下面各题，从题中所给的A、B、C、D四个选项中，选出最佳选项，并在答题卡上将该项涂黑。
21. It’s ______ good feeling for people to admire the Shanghai World Expo that gives them ______ pleasure.
A. /; a B. a; / C. the; a D. a; the
22. Lots of rescue workers were working around the clock, ______ supplies to Yushu, Qinghai Province after the earthquake.
A. having sent B. to send C. sending D. to have sent
23. With your help, there is no doubt ______ our plan is meant for will work out successfully.
A. that what B. whether that C. what that D. that whether
