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 train running at the speed of 60 km / hr crosses a pole in 6 sec . what is the length of the train ? 
Options: a ) 356 , b ) 278 , c ) 127 , d ) 100 , e ) 150
Example Output: d

Example Input: Problem: a water tank is four - fifths full . pipe a can fill a tank in 10 minutes and pipe b can empty it in 6 minutes . if both the pipes are open , how many minutes will it take to empty or fill the tank completely ? 
Options: a ) 6 , b ) 9 , c ) 10 , d ) 12 , e ) 15
Example Output: d

Example Input: Problem: a train is running at a speed of 40 km / hr and it crosses a post in 17.1 seconds . what is the length of the train ? 
Options: a ) 190 metres , b ) 160 metres , c ) 200 metres , d ) 120 metres , e ) 250 metres
Example Output:
a