单选题 By two o'clock the tide which had reached an all-time high was beginning to______.

【正确答案】 A

【答案解析】解析：句意：直到两点这场空前绝后的洪水才开始消退。recede“倒退”；reverse“颠倒，倒转”；return“返回”；retire“退休”。根据句意，A为答案。