from the top of the mountain the citizens find the city is not it used to be.A. Seen th

问题补充：

from the top of the mountain, the citizens find the city is not it used to be.

A. Seen, that, what

B. See, what, that

C. To see, what, that

D. Seeing, that, what

答案：

A. Seen, that, what

B. See, what, that

C. To see, what, that

(答案→)D. Seeing, that, what

解析：考查非谓语动词及定语从句。句意：从山顶上看去，市民们发现已经不是过去的样子了。宾语从句中不缺少句子成分，故用that引导。下一级从句中缺少逻辑表语，故引导词用what。现在分词表示正在进行的伴随性动作，结合语境而可知选D。