单选题If the coolant temperature of a closed cooling water system for a diesel engine gradually increases, the trouble usually is （）Aa broken shaft on the freshwater pumpBan excessive accumulation of scale exchangerCan incorrect thermostatic element operating rangeDlube oil in the cooling water
单选题
If the coolant temperature of a closed cooling water system for a diesel engine gradually increases, the trouble usually is （）
A
a broken shaft on the freshwater pump
B
an excessive accumulation of scale exchanger
C
an incorrect thermostatic element operating range
D
lube oil in the cooling water
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