公园偶遇一美国老师，妈妈只听到二人谈论volcano 和earthquake,没太听懂他们说的，晚上回来问，说：volcano explode lava, a little pieces of stone come out of the volcano,and some rocks near the volcano are very light ,they can float on the water, "that's right", the teacher said. ，汗啊，我只能在旁边傻笑
