What does “se dan la mano” mean a) they shake our hand b) they shake each other’s hand c) you shake their hand d) we shake each other’s hand

B) they shake each other's hand
The verb in this sentence,"se dan", comes from "darse", which is a reciprocal verb (verbo recíproco) and these verbs always talk about something that the speakers are mutually doing, so the other options wouldn't be correct because: 1) They aren't referring to the 3rd person of plural, 2) They aren't doing a reciprocated action. 
Hope this helped you :)

Hey there,

A) They shake our hand - ellos sacuden nuestra mano
B) They shake each other's hand - se dan la mano
C) You shake their hand - agitas su mano
D) We shake each other's hand - Nos damos la mano a los demás

Thus the answer is B.

Hope this helps :D

~Top♥

Do you need me to translate or write the facts and opinions of the family union? im sorry i just couldnt tell

Vivimos is the answer hope it : )