Always * * * shake hands ten times, every two people shake hands once, and everyone shakes hands with the other four people. First, take the initiative to reach out and count the times, and passively ignore them to meet the requirement of shaking hands between every two people in the topic.

Use a, b, c, e and d to represent five people:

AB, AC, AD, AE: Strong and active handshake (A)

BC, BD, BE: Tao Tao takes the initiative to shake hands (B)

CD, CE: Lili shakes hands actively (c)

De: Niu Niu shakes hands actively (D)

Beibei did not take the initiative to shake hands, but passively shook hands with four other people:

That is, shake hands with Zhuang Zhuang, Tao Tao, Lili and Niu Niu once each, ***4 times.