Euler's buckling load is the maximum compressive load hat a slender column can resist before bending or buckling. It is proportional to the Young's modulus of the column material, as well as the cross-sectional area of the column. It is inversely proportional to the square of the length of the column:
Where P_cr is the Euler's buckling load, E is the Young's modulus of the material, L is the length of the column and I is the area moment of inertia.
Since column A buckles more easily than column B, then the Euler's buckling load of column B must be greater than that of column A. This situation could be produced whenever column A has a smaller cross-sectional area, a smaller Young's modulus, or a greater length, or a combination of those factors.
Since the Euler's buckling load depends on various factors, we cannot be sure that column A has a smaller cross-sectional area, a smaller Young's modulus or a greater length than column B. The only statement that must be true, is: