Answer:
B. an observational study with lurking variables that may explain the association.
Explanation:
Observational Study is the study involving, collection of sample data, & observing the variations / trends in it, without any experimental manipulation.
The study given tries to observe the impact of computer, video games on depression vulnerability, violence among adolescents. The study observes the natural data of collected sample adolescents, without any experimental changes.
It also has many lurking variables which may effect the independent variables (gaming) & dependent variables (depression & violence). Eg : Parents state of mind & relationship with adolescents, digital medium usage by peer group. As, both given variables might effect the study variables & explain their relationship