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: the radius of a circular wheel is 1.75 m , how many revolutions will it make in traveling 1 km ?
Options: ['a ) 1000', 'b ) 2788', 'c ) 2677', 'd ) 2899', 'e ) 2771']

Ex Output:
a

Ex Input:
Problem: a man can row upstream at 5 kmph and downstream at 25 kmph , and then find the speed of the man in still water ?
Options: a ) 15 , b ) 77 , c ) 30 , d ) 88 , e ) 34

Ex Output:
a

Ex Input:
Problem: machine z takes 2 more hours than machine b to make 20 widgets . if working together , the machines can make 25 widgets in 3 hours , how long will it take machine z to make 40 widgets ?
Options: a ) 5 , b ) 6 , c ) 8 , d ) 10 , e ) 12

Ex Output:
e