单选题 They are well ______ with each other since they once studied in the same university.
A. identified B. recognized C. acknowledged D. acquainted

【正确答案】 D
【答案解析】identify：认出，鉴定；recognize：认出；acknowledge：承认；be acquainted with sb．：与某人见过面，熟识。从句意可知本题选D。