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: r is the set of positive even integers less than 20 , and s is the set of the squares of the integers in r . how many elements does the intersection of r and s contain ? 
Options: ['a ) none', 'b ) two', 'c ) three', 'd ) five', 'e ) seven']
Example Output: c

Example Input: Problem: two passenger trains start at the same hour in the day from two different stations and move towards each other at the rate of 22 kmph and 21 kmph respectively . when they meet , it is found that one train has traveled 60 km more than the other one . the distance between the two stations is ? 
Options: a ) 288 , b ) 516 , c ) 877 , d ) 278 , e ) 178
Example Output: b

Example Input: Problem: p is able to do a piece of work in 10 days and q can do the same work in 12 days . if they can work together for 5 days , what is the fraction of work left ? 
Options: a ) 7 / 12 , b ) 5 / 12 , c ) 1 / 12 , d ) 3 / 12 , e ) 1 / 2
Example Output:
c