单项选择题
A.fy/fB.fy/fuC.f/fuD.f/fy
A.α0< 1B.α0=1C.α0>1D.α0>2
A.4.2B.5.7C.6.2D.6.5
A.0.75,0.8B.0.8,0.75C.0.75,0.75D.0.8,0.8
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