单选题Which of the following statements concerning fire-tube boilers is correct?（）ACombustion gases flow through the tubesBFlames impinge on the tubesCCombustion occurs in the tubesDWater flows through the tubes
单选题
Which of the following statements concerning fire-tube boilers is correct?（）
A
Combustion gases flow through the tubes
B
Flames impinge on the tubes
C
Combustion occurs in the tubes
D
Water flows through the tubes
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