非磁性物质内部无磁畴结构，而（）物质的相对磁导率大大于1。
参考答案：铁磁性
--- I called Nina several times, but she didn't answer.
--- Of course, she ____________ London for a visit. [ ]
A. has been to
B. has gone to
C. has been in
D. had gone to
[问题4] 电子商务的含义是什么如何分类
