单项选择题
A.24:1B.50:1C.90:1D.100:1
A.20:1B.22:1C.24:1D.30:1
A.PS0.2MpaB.CS0.4MpaC.PS0.5MpaD.CS0.2Mpa
A.CS0.2MpaB.PS0.2MpaC.PS0.5MpaD.CS0.3Mpa
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