In this task, you need to answer the given multiple-choice question on the physics. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Example Input: Problem: two trains of equal length , running with the speeds of 60 and 40 kmph , take 55 seconds to cross each other while they are running in the same direction . what time will they take to cross each other if they are running in opposite directions ?
Options: a ) 10 sec , b ) 16 sec , c ) 13 sec , d ) 67 sec , e ) 11 sec
Example Output: e

Example Input: Problem: 9 spheres of the same size are made from melting a solid cylinder of 16 cm diameter and 12 cm height . what is the diameter of each sphere ?
Options: ['a ) 4 cm', 'b ) 6 cm', 'c ) 8 cm', 'd ) 10 cm', 'e ) 12 cm']
Example Output: c

Example Input: Problem: a man can do a piece of work in 6 days , but with the help of his son , he can do it in 3 days . in what time can the son do it alone ?
Options: a ) 5 , b ) 7 , c ) 6 , d ) 8 , e ) 9
Example Output:
c