单项选择题
A.r1=1.5,r2=1.5B.r1=1,r2=1C.r1=0.5,r2=0.5D.r1=1.5,r2=0.7
A.2.42B.2.40C.2.37D.2.35
A.0.970B.0.965C.0.952D.0.945