单项选择题

  如图所示的结构中,FPcri(i=1,2,3,4)为临界荷载,EI=常数,k为弹簧刚度,则______。
   

A.FPcr1>FPcr2>FPcr3>FPcr4
B.FPcr2>FPcr3>FPcr4>FPcr1
C.FPcr1>FPcr4>FPcr3>FPcr2
D.FPcr4>FPcr3>FPcr2>FPcr1