一个平行四边形的面积是48平方厘米，与它等底等高的三角形的面积是（ ）平方厘米。
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I want to know how much _____ about the table manners around the world. [ ]
A. do they know
B. they know
C. did they know
D. have they knows
葡萄糖是（）
A.五碳醛糖
B.六碳醛糖
C.甲基五碳醛糖
D.六碳酮糖
E.糖醛酸
