Mike lives in Guangzhou. His friend Tom lives in Xi'an. This winter, Tom came to Guangzhou to see Mike. They were very happy to see each other. They asked a lot about each other's family and work. They talked about the weather in their cities, too. Guangzhou is quite warm in winter. It doesn't snow in winter in Guangzhou. Some people in Guangzhou have never seen snow. In Xi'an, it often snows in winter. Children like to play snowball fight and make snowmen. That is great fun. Mike hoped to visit Xi'an next winter.

一个几何体的正视图和俯视图如图所示，其中俯视图是边长为2 $\sqrt{3}$ 的正三角形及其内切圆，则侧视图的面积为（   ）

下面四幅图中反映电动机工作原理的是（　　）