Explanation:

In a circle of n different persons, the total number of arrangements possible = (n – 1)!
n(S) = (12 – 1) = 11 !
Taking two persons as a unit, total persons = 11
Therefore no. of ways for these 11 persons to around the circular table = (11 – 1)! = 10!
In any unit, 2 particular person can sit in 2! ways.
Hence total number of ways that any three person can sit,
=n(E) = 10! * 2!
Therefore P (E) = probability of three persons sitting together = n(E) / n(S)
= (10! * 2!)/11! = 2/11.

Hence, option 1 is the correct answer.