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: two trains 120 m and 160 m long run at the speed of 60 km / hr and 40 km / hr respectively in opposite directions on parallel tracks . the time which they take to cross each other is ? 
Options: a ) 10.9 , b ) 10.7 , c ) 10.3 , d ) 10.08 , e ) 10.2
Example Output: d

Example Input: Problem: calculate the circumference of a circular field whose radius is 8 centimeters . 
Options: a ) 17 π cm , b ) 18 π cm , c ) 1 π cm , d ) 16 π cm , e ) 6 π cm
Example Output: d

Example Input: Problem: a train running at the speed of 60 km / hr crosses a pole in 42 seconds . what is the length of the train ? 
Options: a ) 120 metres , b ) 700 metres , c ) 324 metres , d ) 828 metres , e ) 600 metres
Example Output:
b