题目

两个大小不同的圆组成组合图形，组合图形怎样组合有一条对称轴？组合图形怎样组合有无数条对称轴？画一画。 答案：答：组合图形的圆心不重合时有一条对称轴；圆心重合时有无数条对称轴。 示例： AIDS is said__________the biggest health to people in that area over the past few years. A.that is        B.to be       C.that it has been      D.to have been