A:FeO
B:Fe2O3
C:Fe3O4
D:FeO和Fe2O3
Research findings have shown that about 20 percent of people only 10 percent can be ____(分类) as “early birds”.
音乐会上男低音独唱时由女高音轻声伴唱,下面说法正确的是 ( )
任意一个纬线圈都可以把地球分成两个半球,这种说法是