答案及解析：[单选题]The main types of social networking services are those that contain category places (such as former - 软件水平题库- 答案窝(daanwo.com)-大学生作业答案及考资分享平台

问题：

[单选题] 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