单项选择题
A.μN=0.806<0.95,满足三级要求 B.μN=0.806<0.85,满足二级要求 C.μN=0.83<0.9,满足三级要求 D.μN=0.76<0.8,满足二级要求
A.0.438 B.0.572 C.0.621 D.0.554
A.R=575.07kN B.R=584.56kN C.R=602.27kN D.R=592.52kN