單項(xiàng)選擇題矩形截面梁,截面寬b=30mm,高h(yuǎn)=40mm,危險(xiǎn)截面的彎矩等于960N·m,剪力等于576KN,最大正應(yīng)力等于()

A.800N/mm2
B.120N/mm2
C.160N/mm2
D.480N/mm2