A:试管a中气体是O2
B:试管b下方导线接电源正极
C:氧元素由游离态变为化合态
D:产生的H2和O2的质量比为2:1
陆半球上不能看见的大洲是( )
Last year my father ______ the city where he was born.
既能消化淀粉又能消化脂肪的消化液是