The proper use of a conclusion is to restate the main argument or claim so I would go with A). To reinforce the primary claim.
After all, we did love playing a prank on him.
Answer:
He had an affair.
Explanation:
He is trying really hard to make up for it.
The answer is most likely "The order of its main points"
Loss of individualism. If everyone is the same, everything is the same day after day in a cubicle with no windows or distinct decor differing from one room to the next, there is no individuality