The cross－head shoes are white metal _____.

Vents are led from the engine to head tank _____ from the cooling water.

Valves in the cylinder head of a diesel engine are opened by the direct action of the ____

A built－up exhaust valve is one in which ______.A.the stem and heads are made of different

The cast iron _____ for the cross－head are attached to the top section and seal off the cr

If you are at a crossing where the traffic has green light, you should ______.A．make sure

Almost all metals are good conductors, silver______ the best of all.A．isB．beingC．has beenD