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

问题补充：

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

A. pick up

B. take up

C. set up

D. make up

答案：

(答案→)A. pick up

B. take up

C. set up

D. make up

解析：考查介词短语：A. pick up捡起，偶然习得，恢复，接送，B. take up从事，拿起，占据，C. set up建立，D. make up 组成，编造，弥补，化妆，句意：通过和当地人交朋友，一个人可以习得很多他们的语言。选A。