单选题 By the end of this century, the population of the world ______, and so may the population of the small country.
A. will be doubled B. may be double
C. will have to be doubled D. may have been doubled

【正确答案】 D

【答案解析】[解析] 从句子后半部分所用may一词可以确定A、C是不合适的；B中double是形容词，指状态，而不是动态；“也许会翻一番”，也不合适。所以应选may have been doubled。