Which sentences state the research purpose or main activity?

Which sentences state the research purpose or main activity?
A.The experiments were designed to assess...
B.In this study, we used... as a study system to better understand the effects of...
C.Our study revealed ...
D.Few studies have been done on...
正确答案：The experiments were designed to assess...；In this study, we used... as a study system to better understand the effects of...