单选题 ______much has been known about mammary cancer, the precise way to cure of it still remains largely in the realm of testing.
【正确答案】 A
【答案解析】解析：本题考查逻辑关系和连词。“知之甚多”与“仍在测试”构成转折关系，因此选择while，该词置于句首表示“虽然，尽管”。