单项选择题
A.3 B.9 C.12 D.16
A.5.0MPa B.设计强度的100% C.设计强度的70% D.3.0MPa
A.1:2.5 B.1:2 C.1:4 D.1:3
A.0.5% B.1% C.2% D.5%
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