为什么在突出矿井中开采煤层群时，必须首先开采保护层？

系统中雷达状态包括Unknown、Operational（or ON）、Failed（or OFF）、Detached。

Shutdown price（or point，or rule） 停业价格（或停业点、停业原则）

翻译：With Average or With Particular Average（WA or WPA）（）

《煤矿安全规程》规定，开采（）的煤层，严禁任何两个工作面之间串联通风。

煤矿安全规程规定，随矿井通风风流从回风井排出的煤层气最多不能超过（）。

《煤矿安全规程》要求采易自燃和自燃煤层时，采煤工作面必须采用后退式开采。

Every deliberate act of wrongdoing by the master or any of the crew against the ship or cargo，without the authorization or privity of the Shipowner or his agent，is（）.

（）, or drum is used for hauling in or letting out the wires or ropes which will fasten the ship to the shore.

A salvor may be（）the whole or part of the payment due under Salvage Convention to the extent that the salvage operations have become necessary or more difficult because of fault or neglect on his part or if the salvor has been guilty of fraud or other dishonest conduct.

逻辑运算符（AND、NOT、OR）的运算顺序是AND→OR→NOT。

逻辑运算符（AND、NOT、OR）的运算顺序是AND→OR→NOT。