单选题 It is developing a service that will let you create all online identity that can ______ various claims that it will back up.
A. plunge B. assert C. exert D. insert

【正确答案】 B
【答案解析】[解析] A项意为“投入”；B项意为“维护，坚称”；C项意为“运用，施加影响”；D项意为“插入，嵌入”。因此，B选项符合题意。