特种作业人员上岗前必须接受专门的培训,经考试合格取得()证书,方可上岗作业。
A.大学专科学历
B.执业资格
C.职业技能
D.操作资格
参考答案:D
Zhuhou, _______ on the Xiang River, is an important city, second only to Changsha.
A.located
B.locating
C.being located
D.to be located
压力开关的工作原理是什么?