磁性材料按其特性、结构和用途可分为（）材料，（）材料，磁记录材料和磁记忆材料。
参考答案：软磁；永磁（硬磁）
Beijing National Stadium,the showpiece of the Beijing Olympics,has fallen into disuse since the
end of the games, it difficult to make a profit.[ ]
A.make
B.to make
C.making
D.made
长方形楼层板，纵横长短筋哪个在上哪个在下？
