壁式体系采煤法的特点有哪些？（）

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.

The （） is used for hauling in or letting out the wires or ropes.

Vessels must be（）valid certificate of nationality or certificated of registry or license.

逻辑运算符（AND、NOT、OR）的运算顺序是AND→OR→NOT。

壁式体系采煤法有哪些主要特点？较柱式体系相比有何优缺点？

壁式体系采煤法，按采用的采煤工艺不同分为（）、（）、（）采煤法。

倾斜壁式采煤法

逻辑运算符（AND、NOT、OR）的运算顺序是AND→OR→NOT。

采煤工作面沿走向推进，这种采煤法为（）长壁采煤法。