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 length of the bridge , which a train 130 meters long and travelling at 45 km / hr can cross in 30 seconds , is ? 
Options: a ) 288 , b ) 266 , c ) 245 , d ) 277 , e ) 211
Example Output: c

Example Input: Problem: two spherical balls lie on the ground touching . if one of the balls has a radius of 10 cm , and the point of contact is 12 cm above the ground , what is the radius of the other ball ( in centimeters ) ? 
Options: a ) 14 , b ) 15 , c ) 16 , d ) 18 , e ) 20
Example Output: b

Example Input: Problem: a certain car uses 12 gallons of gasoline in traveling 120 miles . in order for the car to travel the same distance using 10 gallons of gasoline , by how many miles per gallon must the car ’ s gas mileage be increased ? 
Options: a ) 2 , b ) 4 , c ) 6 , d ) 8 , e ) 10
Example Output:
a