pigmy hippopotamus

例句：

1. 1.The hippopotamus is a large mammal that lives in rivers and lakes.
   河马是一种生活在河流和湖泊的大型哺乳动物。
2. 2. Pigmy hippos are the smallest members of the hippopotamus family.
   河马是河马家族中最小的成员。
3. 3. The hippopotamus is known for its gentle nature and playful behavior.
   河马以其温和的本性和活泼的行为而闻名。