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【单选题】
尖晶石(MgAl2O4)晶体中含有N个原胞。那么在晶体中有声学波声子和光学波声子分别为几种？
A.
3N,18N
B.
N,7N
C.
3N,21N
D.
7N,21N
参考答案：
参考解析：
刷刷题刷刷变学霸
举一反三
【单选题】Human beings have used tools for a very long time. In some parts of the world you can still find tools that people used more than two million years ago. They made these tools by hitting one stone agai...
A.
disastrous.
B.
unpredictable.
C.
exciting.
D.
colourful.
【多选题】下面对晶体智力的描述正确的是( )
A.
它不依赖于文化和知识，而取决于个人的禀赋
B.
它在发展到人的中年之后有下降的趋势
C.
在人的一生中是稳步上升的
D.
它取决于后天的学习