The discovery of these tombs is for scholars’ studying the history of the Tang Dynasty.A.

问题补充：

The discovery of these tombs is for scholars’ studying the history of the Tang Dynasty.

A. of very important

B. great importance

C. of great significance

D. great significant

答案：

A. of very important

B. great importance

(答案→)C. of great significance

D. great significant

解析：考查： of + 名词，相当于形容词的用法，of great significance = very significant，句意：这些坟墓的发现对研究唐代历史的学者们非常有意义。所以选C。