By the middle of the 21st century, the vast majority of the world’s population in cities

By the middle of the 21st century, the vast majority of the world’s population in cities rather than in the country.
A. are living
B. will be living
C. have lived
D. will have lived

A. are living (答案→)B. will be living C. have livedD. will have lived解析：试题分析：考查时态。根据本句的时间状语by the middle of the 21st century说明是一个将来时。陈述的是在将来的这段时间里所发生的事情，所以使用将来进行时。句意：到21世纪中叶，大部分的人口都将生活在城里而不是在乡下。故B正确。考点：考查时态点评：时态题的考查关键是抓住句中的时间状语。要根据时间状语来选择合适的时态，在平时的学习中要注意积累有关时态的用法和各种时态的特殊之处。

就是这个解释