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: the sector of a circle has radius of 21 cm and central angle 180 o . find its perimeter ?
Options: a ) 91.5 , b ) 92 , c ) 108 , d ) 94 , e ) 95
Example Output: c

Example Input: Problem: a man is standing on a railway bridge which is 180 m long . he finds that a train crosses the bridge in 20 seconds but himself in 8 seconds . find the length of the train and its speed
Options: a ) 50 km , b ) 52 km , c ) 54 km , d ) 56 km , e ) 58 km
Example Output: c

Example Input: Problem: a river 3 m deep and 32 m wide is flowing at the rate of 2 kmph the amount of water that runs into the sea per minute is ?
Options: a ) 4500 , b ) 3200 , c ) 3400 , d ) 2761 , e ) 2882
Example Output:
b