物体的主视图，左视图，俯视图都相同的是______．
正方体的三视图都为正方形；
球的三视图都是圆．
已知△ABC∽△A1B1C1，AB：A1B1=2：3，则S△ABC与S△A1B1C1之比为______．
—Let's listen to the weather forecast.
—______. [ ]
A. I think so
B. Good idea
C. Yes, please
D. Yes, it is.
