Question

What does “se dan la mano” mean

Answer 1

Hey there,

Answer:

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

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Answer 2

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 :)