单选题Valve cages are used on some large diesel engines to （）Areduce wear on the valve stemBpermit the use of alloy valve seat materialsCreduce heat transfer from the valve seatDfacilitate valve removal for servicing
单选题
Valve cages are used on some large diesel engines to （）
A
reduce wear on the valve stem
B
permit the use of alloy valve seat materials
C
reduce heat transfer from the valve seat
D
facilitate valve removal for servicing
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