Answer:
D. simple main effect of gender.
Step-by-step explanation:
A simple main effect refers to the effect that one independent variable has at various different levels of a second independent variable. In this example, Reba is examining the interaction between age and gender. However, she mainly focuses on the effect of a single variable (gender) at various levels of a second variable (different ages). This type of research allows researchers to have a more complete view of the phenomenon at hand.