单项选择题
A.搅拌脱气B.充氮脱气C.真空脱气D.加热脱气
A.13:1B.14.5:1C.15:1D.15.5:1
A.6:1~8:1B.15:1~20:1C.8:1~10:1D.10:1~15:1
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