容器施工动火时，必须按规定吹扫干净，保证氧气含量为（）才可动火。
A、≦20.5%
B、≦22%
C、≦25%
参考答案：A
It is good ________ for an Arab to stand ________ his friend when they are talking.
A．manners; close to
B．manner; close to
C．manners; closely to
D．manner; closed to
下列哪些作业属于特种作业（）.
A.登高作业
B.游泳
C.清理聚合釜
D.给锅炉加水
