问题
单项选择题
Be quiet! They （） a meeting in the next room.
A.are having
B.have
C.were having
D.will had
答案
参考答案：A
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Be quiet! They （） a meeting in the next room.
A.are having
B.have
C.were having
D.will had
参考答案：A
表示列向量αi的转置，i=1，2，…，n．