问题补充：
It is convenient for people to work by subway. It’s said that The Line 4 subway in Chengdu by the time of .
A. will be built
B. would be built
C. will have been built
D. would have been built
答案：
A. will be built
B. would be built
(答案→)C. will have been built
D. would have been built
解析：句意：人们乘坐地铁上班很方便。据说在成都地铁4号线将在以前建成。由时间状语by the time of 可知该用将来完成时态，又The Line 4 subway是build这一动作的承受着，该用被动语态，所以选C。
