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

问题补充：

—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：

(答案→)A. It must have been

B. They must be

C. That might be

D. 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。