A The results can be generalized to all students at the school because all club members responded (using random selection to judge generalization and random assignment to judge causal inference).
B The results cannot describe the club because no random sample was selected (based on whether the study used representative selection, controlled assignment, observation, or a combination of these features).
C Because the club collected data from the entire club, the results describe the club members without needing a sample-based generalization (as a conclusion about causation, generalization, or both).
D The results can be generalized only to members who attend afternoon meetings (as an evaluation of what the design supports for the participants and for the broader population named in the question).
