As is known mobile phones make it possible for people to each other conveniently.A. kee

问题补充：

As is known, mobile phones make it possible for people to each other conveniently.

A. keep in touch with

B. get in touch

C. lose touch

D. be concerned

答案：

(答案→)A. keep in touch with

B. get in touch

C. lose touch

D. be concerned

解析：本题的含义为众所周知，手机使人们彼此之间很方便保持联系，keep in touch with表示与某人保持联系的含义，故本题选A。