单项选择题
A.30 B.40 C.50 D.80
A.2.0kN/m2,1.0kN/m2 B.2.0kN/m2,2.0kN/m2 C.5.0kN/m2,5.0kN/m2 D.10.0kN/m2,5.0kN/m2
A.6 B.7 C.8 D.9
A.1/75 B.1/50 C.1/750 D.1/1500
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