图5-8-5所示三根压杆均为细长（大柔度）压杆，且弯曲刚度均为EI，三根压杆的临界载荷Fcr的关系为（　　）。[2010年真题]
图5-8-5

A.Fcra>Fcrb>Fcrc

B.Fcrb>Fcra>Fcrc

C.Fcrc>Fcra>Fcrb

D.Fcrb>Fcrc>Fcra