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

Example Input: Problem: how many kilograms of pure water is to be added to 100 kilograms of a 30 % saline solution to make it a 10 % saline solution . 
Options: a ) 100 , b ) 200 , c ) 300 , d ) 400 , e ) 500
Example Output: b

Example Input: Problem: if m = 3 ^ n , what is the greatest value of n for which m is a factor of 19 ! 
Options: a ) 8 , b ) 10 , c ) 12 , d ) 14 , e ) 16
Example Output: a

Example Input: Problem: a garrison of 400 men had a provision for 31 days . after 20 days 180 persons re - enforcement leave the garrison . find the number of days for which the remaining ration will be sufficient ? 
Options: a ) 65 days , b ) 45 days , c ) 20 days , d ) 16 days , e ) 18 days
Example Output:
c