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: a pipe can fill a cistern in 33 minutes . find the time in which 1 / 11 part of the cistern will be filled ? 
Options: a ) 5 min , b ) 2 min , c ) 3 min , d ) 1 min , e ) 10 min
Example Output: c

Example Input: Problem: two spherical balls lie on the ground touching . if one of the balls has a radius of 10 cm , and the point of contact is 12 cm above the ground , what is the radius of the other ball ( in centimeters ) ? 
Options: a ) 14 , b ) 15 , c ) 16 , d ) 18 , e ) 20
Example Output: b

Example Input: Problem: a train speeds past a pole in 10 seconds and a platform 50 m long in 20 seconds . its length is : 
Options: a ) 30 m . , b ) 40 m . , c ) 60 m . , d ) 50 m . , e ) 70 m .
Example Output:
d