單項選擇題Economics, several courses of which I have taken thus far,（）to be difficult but useful for almost all students。
A.prove
B.havebeenproved
C.proves
D.areproved
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1.單項選擇題A large crowd（）expected at the football match。
A.is
B.be
C.are
D.will
2.單項選擇題The school staff（）gathered to hear the president speak。
A.is
B.be
C.are
D.will