They always communicated with each other on the Internet but they never met him . A. back

问题补充：

They always communicated with each other on the Internet, but they never met him .

A. back to back

B. heart to heart

C. face to face

D. side to side

答案：

A. back to back

B. heart to heart

(答案→)C. face to face

D. side to side

解析：短语辨析。back to back背靠背，连续； heart to heart率直的，诚实的； face to face 面对面的，对立的 ；side to side 边对边。句意：他们总是在互联网上相互沟通，但是他们从来没有面对面见过。故选C。