The students in a certain physical education class are on either the basketball team or the tennis team, are on both these teams, or are not on either team. If 15 students are on the basketball team, 18 students are on the tennis team, 11 students are on both teams, and 14 students are not on either of these teams, how many students are in the class?

The students in a certain physical education class are on either the football team or the basketball team, are on both these teams, or are not on either team. If 12 students are on the football team, 15 students are on the basketball team, 8 students are on both teams, and 9 students are not on either of these teams, how many students are in the class?

“Full speed ahead” and “Full speed astern” are（）given by the officers or the pilots.

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.

If we carry out our plan with（）we will surely achieve our goal sooner or later.

逻辑运算符（AND、NOT、OR）的运算顺序是AND→OR→NOT。

A 20-meter power-driven vessel pushing ahead or towing alongside will display（）.

逻辑运算符（AND、NOT、OR）的运算顺序是AND→OR→NOT。