A.
B.
C.
D.
[单选题]A.B.C.D.
[单选题]A.AB.BC.CD.D
[单选题]A.28500B.28800C.27000D.28650
[单选题]A.420B.450C.840D.900
[单选题]A.B.3.419C.D.17.09
[多选题]A.B.C.D.
[单选题]A.8kNB.5kNC.3kND.13kN