Answer:
a.) the effect of one independent variable depends on the levels of the second variable
Explanation:
In regression, an interaction effect comes to play whenever the effect that an independent variable has on a dependent variable changes, as regards to value(s) of other independent variables( one or more variables). The variables that give interaction effect as a result of interaction with each other is reffered to as "interacting variables" For instance, in a research whereby how "Male gender versus female gender" and their " dieting B and dieting D" influence their " weight loss" There would be interaction effect in a situation where by a " female gender" that operate on " diet B" shed more weight compare with " male gender" that operate on " diet B". It should be noted that two variables are said to interact when the effect of one independent variable depends on the levels of the second variable