简述布尔算符（OR）的作用。

OR指令的作用是: 。( )

简述学前儿童观察的作用。

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.

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

逻辑运算符（AND、NOT、OR）的运算顺序是AND→OR→NOT。

学前儿童科学教育中，常用的观察方法有比较性观察、（）、长期系统性观察、间或性观察、室内观察与室外观察等几种。

逻辑运算符（AND、NOT、OR）的运算顺序是AND→OR→NOT。