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: the curved surface of a sphere is 64 cm 2 . find its radius ?
Options: ['a ) 8', 'b ) 3', 'c ) 4', 'd ) 9', 'e ) 7']
Example Output: c

Example Input: Problem: if 22 men do a work in 55 days , in how many days will 10 men do it ?
Options: a ) 121 , b ) 123 , c ) 119 , d ) 125 , e ) 127
Example Output: a

Example Input: Problem: two diesel trains of length 120 m and 280 m are running towards each other on parallel lines at 42 kmph and 30 kmph respectively . in what time will they be clear of each other from the moment they meet ?
Options: a ) 10 sec , b ) 30 sec , c ) 40 sec , d ) 20 s , e ) 50 sec
Example Output:
d