Answer:
A. What were the major outcomes of the Vietnam War? is the correct answer.
Explanation:
Outcome is a synonym with result or product, meaning what happened after the war. The second questions asks about the opposite, about antecedents. Letter C is inquiring about parallel events, things that were happening at the same time in a different context. Letter D could be important for the context, as long as they are linked in someway to the outcomes. If not, it could be unnecessary to mention them. The only question that asks about the results is option A.