—The poor people lived near the highway.— very noisy.A. It must have beenB. They must beC.

—The poor people lived near the highway.
— very noisy.

A. It must have been
B. They must be
C. That might be
D. There must be

(答案→)A. It must have beenB. They must beC. That might beD. There must be解析：根据句子的时态应该是过去时，因此排除B、D，再根据代词的用法，it可以用来指代环境，而that不行，因此选A。

对的，就是这个意思