单项选择题
A.＜0.003MPaB.＜0.004MPaC.＜0.005MPaD.＜0.006MPa
A.＞99.7%B.＞99.9%C.＞99.6%D.＞99.8%
A.4〜12hrB.4〜24hrC.12〜24hrD.4〜8hr
A.≥4hrB.≥2hrC.≥6hrD.≥8hr
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