When you name two congruent triangles with the letters of the vertices, you have to keep the order of the corresponding vertices. That means, that when you say triangle ABC is congruent to DEF, the corresponding congruent angles are A = D, B = E, and C = F. regarding the sides, segment AB = segment DE, segment BC = segment EF, and segment CA = segment FD. Then, the answer is that, of the four options, the one that is not true is the option b, because as we already said the corresponding equal angle C is F, not E.