The main types of social n（2014年下半年信息系统项目管理师上午综合知识真题解析）
The main types of social networking services are those that contain category places (such as former school year or classmates), means to connect with friends (usually with self-description pages), and a recommendation system linked to （）.
A、net
B、interests
C、others
D、trust
参考答案： D
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