By making friends with the native speakers one can a lot of their language. A. take upB.

问题补充：

By making friends with the native speakers, one can a lot of their language.

A. take up

B. set up

C. pick up

D. put up

答案：

A. take up

B. set up

(答案→)C. pick up

D. put up

解析：考查短语辨析。take up从事，set up建立， pick up 捡起，偶然学到， put up搭起，句意：通过和本地人交朋友，一个人就会偶然学到他们的语言。故选C。