A:What do you like doing?
B:What does he like doing?
计算下列化学方程式中物质之间的质量比:
2KMnO4=△ K2MnO4+MnO2+O2↑
2H2O2H2↑+O2↑
地球上分布最广、数量最多且具有根茎叶的植物类群是( )