单项选择题
The pH value of water in a diesel engine closed cooling water system should be maintained between （）.
A.60 to75 B.80 to 95 C.100 to 115 D.120 to 135
单项选择题 Indirect cooling of fuel injector nozzle holders for diesel engines is accomplished primarily by （）.
单项选择题 In a diesel engine cooling water system, a pH of 60 indicates a/an （）.
单项选择题 Which of the following statements concerning fire-tube boilers is correct?（）
