When one makes new friends don’t forget old ones.A. to come up withB. losing sight ofC.

问题补充：

When one makes new friends, don’t forget old ones.

A. to come up with

B. losing sight of

C. to keep track of

D. keeping in touch with

答案：

A. to come up with

B. losing sight of

(答案→)C. to keep track of

D. keeping in touch with

解析：come up with意思是提出、 想出 lose sight of看不见 keep track of保持联系 keep in touch with保持联系。有了新朋友，别忘了老朋友。故选C。