Most people don't think of a stamp as a receipt, but that is________it really is a proof of just how much money you have paid in advance for mail delivery.
【正确答案】 B
【答案解析】解析：经分析可以看出A、C、D选项都与题意不符，只有B选项符合句子的意思：“绝大多数人都不会把邮票视作一种收据，但这也更能说明为什么它可以证明你已经提前支付了邮资。”