单项选择题
A.F1=35.5kN,F2=10.76kN,F3=7.5kN B.F1=22.5kN,F2=8.96kN,F3=12.4kN C.F1=35.5kN,F2=8.96kN,F3=7.76kN D.F1=35.5kN,F2=25.2kN,F3=7.76kN