问题补充:
It is reported that two schools, are being built in my hometown, will open next year.
A. they both
B. which both
C. both of them
D. both of which
答案:
A. they both
B. which both
C. both of them
(答案→)D. both of which
解析:both of which are being built in my hometown为非限制性定语从句,其中的which指代前面的two schools。