Explain why the existence of an interaction limits the interpretation of the main effects in a two-factor study

What will be an ideal response?

The existence of an interaction means that the effect on one factor depends on the levels of the second factor. Thus, the effect of the factor is not consistent but rather varies as the second factor changes. The main effect for the factor is obtained by averaging over all of the different effects and, therefore, probably does not accurately describe any of them.