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'.

Ex Input:
Problem: some persons can do a piece of work in 8 days . two times the number of these people will do half of that work in ?
Options: a ) 2 , b ) 4 , c ) 5 , d ) 6 , e ) 8

Ex Output:
a

Ex Input:
Problem: a cistern is normally filled in 10 hrs , but takes 2 hrs longer to fill because of a leak on its bottom , if cistern is full , how much time citern would empty ?
Options: a ) 10 hours , b ) 20 hours , c ) 60 hours , d ) 40 hours , e ) 50 hours

Ex Output:
c

Ex Input:
Problem: a bicycle wheel has a diameter of 0.75 m . how many complete revolutions does it make in 1 km ?
Options: a ) 424 , b ) 448 , c ) 1408 , d ) 710 , e ) 223

Ex Output:
a