The main bearing shells are made of steel with a lining of bearing metal which may be white metal, copper-lead or aluminum-tin alloy What is the meaning of “which” in the sentence above?（）

道岔主线 main line of turnout

主线为（），侧线向主线的左侧或右侧分支的道岔叫单开道岔。

高速铁路车站道岔端部距桥台尾边缘的距离不宜小于（）m。

In most WANs, the network contains numerous cables or telephone lines, each one connecting a pair of

港口枢纽运输组织与铁路枢纽运输组织有何异同？

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（）.

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.

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

道岔中心 center of turnout

单车道岔 simple turnout

铁路车站及枢纽的能力是铁路运输能力的主要组成部分。