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