In the formula Pcr= ( frac{ sigma_c A}{1+a( frac{L}{K_{xx}})} ) what is Kxx?

In the formula Pcr= ( frac{ sigma_c A}{1+a( frac{L}{K_{xx}})} ) what i

1.	In the formula P_cr= ( frac{ sigma_c A}{1+a( frac{L}{K_{xx}})} ) what is K_xx?
A.	Radius of cylinder
B.	Constant
C.	Radius of gyration
D.	The radius of the big end
Answer» D. The radius of the big end