物料流经胶体磨磨头的声音时大时小，属于异常噪音。
参考答案：错
解析：物料流经胶体磨磨头的声音时大时小，属于正常现象。
费尔巴哈
--Are you free in July? --No, I（）with my parents in July.
A.stay
B.stayed
C.have stayed
D.am staying
