挑战习题
1/5单选题
难度:

1.在化学反应前后,以下各项一定不会发生变化的是①原子种类 ②元素种类 ③分子种类 ④物质种类
A ①②
B ①③
C ②③
D ②④
提示1:
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正确答案:QQ==
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