Many people who simply enjoy listening to popular music do not realize that it has been used to express religious and political messages.
Conclusion
Many people who simply enjoy listening to popular music do not realize that it has been used to express religious and political messages.
Intermediate Conclusion (After all)
Popular music has repeatedly been adopted by social movements to express their viewpoints.
Evidence (since)
[Popular music] has the potential to contribute to the "conversion" of nonmembers to the movement's position, as well as to raise the morale and to express the solidarity of the movement's participants.
Evaluate
This is a three-layer argument. The phrase "after all" tells us that what follows is support for the sentence before it — so the first sentence is the main conclusion and the "after all" clause is an intermediate conclusion. Within that clause, the word "since" introduces even deeper support — the evidence that feeds into the intermediate conclusion.
The chain flows upward: music can convert/raise morale/express solidarity (premise) → social movements have adopted music (intermediate conclusion) → people don't realize music carries these messages (main conclusion). On Main Conclusion questions, identify the claim that everything else supports but that itself supports nothing further.
Goal
Look for an answer that captures the main conclusion — the first sentence about people not realizing popular music has been used for religious and political messaging. Watch out for answers that restate a premise or the intermediate conclusion instead.