The elastic buckling stress for thin flat plate of length L, depth d and thickness t simply supported along four edges and loaded by bending stress distribution is given by

• A. f_cr = ²E/k[12(1- ²)(d/t)²].
• B. f_cr = ²E/k[12(1+ ²)(d/t)²].
• C. f_cr = k ²E/[12(1+ ²)(d/t)²].
• D. f_cr = k ²E/[12(1- ²)(d/t)²].