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Seamless mild steel is used for steam (also copper for moderate pressure and temperature), h-pair, feed discharge and all oil fuel pressure pipingsAccording to the above sentence, which of the following statements is not true?（）
A:Both seamless mild steel and copper may be used for middle pressure steam
B:"hpair" means high pressure air
C:The feed piping of the boilers can be made of seamless mild steel
D:All oil pipings are made of mild steel

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出自：海船船员证

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