单项选择题
A.5% B.10% C.15% D.20%
A.30℃ B.40℃ C.50℃ D.60℃
A.0.25～0.35% B.0.35～0.55% C.0.15～0.55% D.0.15～0.35%
A.非金属软垫 B.自紧式垫片 C.金属垫片 D.金属与非金属组合垫片
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