问题
单项选择题
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
答案
参考答案：D
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。