表达式SUBSTR（"河北师大计算机教学部"，7，4）的值为（）。

万方数据库使用布尔逻辑算符anD./or/not.其中A.anD.B表示（）。

在VFP中，对于数据库表使用INDEXON命令可以创建的索引类型有（）。

命令LEFT("123456789"，LEN("计算机"))的结果是（）。

Vfp6.0数据库是关系型数据库系统（）

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。

逻辑运算符（AND、NOT、OR）的运算顺序是AND→OR→NOT。