问题：
[单选] The mechanical efficiency of an engine （） because losses occur in the form of friction.
is always less than 100%。is always more than 100%。is always equal to 90%。is always less than 90%。
问题：
[单选] The needle valve in a fuel valve will （） when the fuel pressure action on the needle valve tapered face exerts a force lower than that of the spring compression.
be jammed。be opened。be seated。be broke。
问题：
[单选] The needle valve in the injector （） at a pre-set pressure which ensures that the fuel will atomize once it enters the cylinder.
will lift。will be lifted。will close。will be closed。
问题：
[单选] The needle valve will open when the fuel pressure acting on the needle valve （） exerts a sufficient force to overcome the spring compression.
tape face。tapered face。surface。thinner face。
问题：
[单选] The oil is drawn from a drain tank through （）, one of a pair of pumps, into one of fine filters.
a strain tank。a head tank。a service tank。a strainer。
问题：
[单选] The oil quantity for bearing lubrication should be applied in such an amount as to be sufficient to carry away the （） caused by the friction at the bearings.
acids。additives。heat。gear。
问题：
[单选] The operating diesel generators will have their exhaust temperatures, cooling water and lubricating oil temperatures and pressures （） in much the same way as for the main engine.
to be kept。logged。changed。has remained。
问题：
[单选] The operation between two fuel injections is called a （）.
turning cycle。working cycle。working hour。working stroke。
问题：
[单选] The operation between two fuel injections is called a working cycle, which consists of a fixed sequence of eventsWhat does "which" mean in this sentence?（）
a working cycle。the operation。two fuel injections。event。
问题：
[单选] The outside diameter of the pipe is （） the diameter of the bore of the piston rod, the result being that an annular space formed between the piston rod and the pipe.
less than。greater than。equal to。twice larger tha。
