单项选择题
A.回车 B.8 C.E D.a
A.(BH3-bh3)/12 B.(BH2-bh2)/6 C.(BH3-bh3)/(6H) D.(BH3-bh3)/(6h)
A.σx=σy,σxy≠0 B.σx=σy、τxy=0 C.σx≠σy,τxy≠0 D.σx=σy=σxy