The old city wall in the Ming Dynasty.
A. was been built
B. has been built
C. was built
D. had been built
网友回答
A. was been built
B. has been built
(答案→)C. was built
D. had been built
解析：考查时态和语态。句意“那些老城墙建于明朝。”根据句意可知，应该用一般过去时，wall和build之间是动宾关系，用被动语态。故选C。