Good job yezz...
I went for C... did't bother to check for 11 x 11
AB and BA are 2-digits integers and AB*BA=CDE, where CDE is a 3-digits integer. What is AB?
(AB) ( A^2+B^2) (AB) = CDE
THE ONLY USEFULL INFORMATION IS THE UNITS DIGIT OF THE PRODUCT IE: E = (AB)
AND C COULD = (AB) AND THUS C =E =A OR C = (AB) + ANY REMAINDER FROM ( A^2+B^2)
AB=E,A=E THUS B = 1 and no information can be deducted about A
A = C NOT SUFF
TOGETHER STILL NOT SUFF
MY ANSWER IS E