A Survey parents about music preferences without measuring spatial reasoning (as a claim evaluated from the study design, target population, and alternative explanations for the observed pattern).
B Compare students who already chose music with students who dislike music (as an interpretation that respects the limits created by selection, assignment, measurement, and unmeasured variables).
C Randomly assign interested eligible students to the music class or to a wait-list comparison group, then compare score gains (as a conclusion limited by the design and possible confounding).
D Measure scores once after the class and assume differences are caused by music (based on the data-collection process and whether the design can rule out confounding or support generalization).
