In this task, you need to provide the correct option for a given problem on probability from the provided options.

Example Input: Problem: when 3 fair coins are tossed together , what is the probability of getting 2 tails ? 
Options: a ) 1 / 2 , b ) 1 / 3 , c ) 1 / 4 , d ) 3 / 4 , e ) 2 / 3
Example Output: a

Example Input: Problem: a coin is tossed 3 times . what is the probability of getting exactly 2 heads ? 
Options: a ) 1 / 2 , b ) 1 / 4 , c ) 3 / 8 , d ) 5 / 8 , e ) 3 / 16
Example Output: c

Example Input: Problem: if 4 people are selected from a group of 5 married couples , what is the probability that none of them would be married to each other ? 
Options: a ) 1 / 33 , b ) 2 / 33 , c ) 1 / 3 , d ) 16 / 33 , e ) 8 / 21
Example Output:
e