单项选择题

A.Uk3%=1/2[Uk(3-1)%+Uk(2-3)%-Uk(1-2)%]
B.Uk (2-3)%=Uk2%-Uk3%
C.Uk3%=1/3[Uk(3-1)%+Uk(2-3)%-Uk(1-2)%]
D.Uk(1-2)%=1/2(Uk1%+Uk2%)