单项选择题
These piston rings are so badly worn that they must be （）.
A.renewed
B.welded
C.machined
D.chromium-plated
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相关考题
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单项选择题
There should be a lubricating oil （） between the main beatings and the crankshaft.
A.film
B.cap
C.lacquer
D.shell -
单项选择题
There is an injection pump for each cylinder, which is usually operated once every cycle by （） on the camshaft.
A.a gear
B.a cam
C.a rod
D.a miler -
单项选择题
There is a （） system lubricating the running gear and cooling the piston and sometimes lubricating the cylinders.
A.recirculating
B.total loss
C.cooling
D.refrigeration
