下列语句中，标点符号使用无误的一项是（    ）

一辆汽车从甲地驶向乙地以30km/h的速度行驶了 $\frac{2}{3}$ 的路程，接着以20km/h的速度行驶到达乙地，后以36km/h的速度返回甲地，则全程往返中的平均速度 $\overline{v}$ 为（   ）

    There are three people in Yang Yang's family. They like different kinds of food. Yang Yang likes rice a lot. But she doesn't like chicken at all. Her father is from Shanxi. He doesn't like rice at all. He likes chicken and bread very much. Her mother is from Dalian. She doesn't like rice or bread at all. But she likes fish and vegetables a lot. They love each other and help each other.