2. _________ in the daytime for most of the year, the groundhog hibernates in a burrow during winter.

A. Is active

B. That it is active

C. Active

D. While is active

答案：C

分析及考点：考状语的省略结构。全句的主语是groundhog，谓语hibernates。A谓语不能单独存在。B that it is错误结构。D缺从句主语。

省略了什么东西啊?难道连引导词也可以省略的吗?我只知道可以省略be动词和主语啊.请高手指教