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