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【单选题】
The following are the reasons why British coal mining is today called a"sick"industry except（）A.
Britain has used up almost all coal deposits
B.
the demand for British coal has declined
C.
petroleum,water power,and electric power are replacing coal for many purposes
D.
the old British mines are narrow and deep,making it difficult to sue machines fro mining.
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【单选题】供电调度员下达的倒闸和作业命令除遇有危及( )安全的紧急情况外,均必须有命令编号和批准时间;没有命令编号和批准时间的命令无效。
A.
人身及设备
B.
人身
C.
设备
D.
电气