A.应小于1.0 B.应大于1.0 C.应小于2.0 D.应大于2.0
A.4.2m B.4.8m C.3.9m D.4.5m
A.图A.、B.和C. B.图A.、B.和D. C.图B.、C.和D. D.图A.、C.和D.
A.取ξ=ξb B.取As=As' C.使x=2as' D.取ρ=0.8%~1.5%
A.A B.B C.C D.D