磁极定装就是通过磁极螺栓将磁极（）固定在机座上。
参考答案：牢固正确地
-Li Lei, what are you doing for your next vacation?
-Please keep __________. All the students are listening to the teacher.[ ]
A. clean
B. quiet
C. quick
D. healthy
职业中毒的临床类型不包括（）
A.急性中毒
B.慢性中毒
C.亚急性中毒
D.迟发性中毒
E.观察对象
