We Are Studying the Effect of Two Methods of Learning

We are studying the effect of two methods of learning, using bright students and dull students, in a two-way analysis of variance. Interaction between method and level of intelligence would be suggested if we found that

A) method A was better for brights, but not for dulls
B) method A was better for brights and better for dulls
C) there is no difference between method A and method B, but there is a difference between brights and dulls
D) there is no difference between methods, and there is no difference between brights and dulls