单选题 Michael studied hard before the examination in mathematics, and it ______ . He made an A.
A. paid out B. paid off C. paid over D. paid well

【正确答案】 B

【答案解析】[解析] pay off“没有白费”，如：His hard work paid off when he got the promotion, pay out“付出(款项等)”；pay over“正式支付”；pay well“收益高”，“报酬高”。根据题意，B是正确答案。