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.

When loading or discharging dry mud or cement，crew members should use goggles and（）.

Effects which are dutiable or subject to prohibitions or restrictions should be declared in （）.

逻辑运算符（AND、NOT、OR）的运算顺序是AND→OR→NOT。

铝合金时效强化的根本原因是（）

请简述铝合金的时效强化因素。

固溶时效处理是铝合金强化的主要方法之一。

下列哪种铝合金是不能热处理强化的铝合金？（）

铝合金是铝中加入合金元素形成。其中不能进行时效硬化、不可热处理强化，但可冷变形，主要用于容器、管道、低载荷零件、制品及铆钉等的的铝合金是（）。

逻辑运算符（AND、NOT、OR）的运算顺序是AND→OR→NOT。