The main types of social networking services are those that contain category places (such as former school year or classmates),which means to connect with friends (usually with self-description pages),and a recommendation system linked to（）

A.net

B.interests

C.others

D.trust

塑料瓶印刷前最好采用的表面处理的方法是（）。

A.火焰处理

B.电晕处理

C.化学处理

D.溶剂处理