She says efforts on how to improve relationships between foreign and American students have yet to be studied in detail.

A、她说应该努力研究外国学生和美国学生之间的关系。
B、她说如何改善外国学生和美国学生之间的关系尚未被详细研究。
C、她说应该致力于研究外国学生和美国学生之间的关系。