In this task, you need to provide the correct option for a given problem on probability from the provided options.
One example is below.
Q: Problem: in a throw of a coin find the probability of getting a tail ? 
Options: a ) 1 / 2 , b ) 1 / 3 , c ) 1 / 4 , d ) 2 / 5 , e ) 2 / 7
A: a
Rationale: "s = { h , t } e = { t } p ( e ) = 1 / 2 answer is a"
Q: Problem: how many different ways can 2 students be seated in a row of 3 desks , so that there is always at least one empty desk between the students ? 
Options: a ) 2 , b ) 3 , c ) 4 , d ) 6 , e ) 12
A:
a