Final answer:
A factorial design option (D) is being used to measure the effect of exposure to different types of online messages, as well as the role of gender.
Step-by-step explanation:
The researcher is using the same subjects to expose them to three types of online messages to measure the effect of that exposure and wants to know if gender plays a role in terms of the effect of the exposure. This is an D) A factorial design. In a factorial design, multiple independent variables are manipulated to examine their individual and combined effects on the dependent variable. In this case, the independent variables are the three types of online messages and gender, while the dependent variable is the effect of the exposure.