A:MgO2﹣氧化镁
B:2N﹣2个氮元素
C:H+﹣1个氢离子
D:H2﹣2个氢原子
I am a s____. I go to s____ every day.
My uncle and aunt____ ____America.
读安溪某地等高线地形图1及地球公转图2,回答问题.