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. There has been_____ rising demand for grain as_____ industrial material in spite of the nation’s
good harvests.
A. /, an B. a, an C. the, an D. a, /
22. The large, water-spouting statue, called “Merlin” －half lion, half fish－ is the____ of Singapore.
A. symbol B. sign C. signal D. scene
