In this task, you need to answer the given multiple-choice question on geometry. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Example Input: Problem: a 1.5 by 2 rectangle is inscribed in circle . what is the circumference of the circle ? 
Options: ['a ) 2.5 π', 'b ) 3 π', 'c ) 3.5 π', 'd ) 4 π', 'e ) 5.5 π']
Example Output: a

Example Input: Problem: a cylindrical cube of radius 12 cm contains water upto a depth of 20 cm . a spherical iron ball is dropped into the tub and thus the level of water is raised by 6.75 cm . the radius of the ball is : 
Options: ['a ) 7 cm', 'b ) 8.5 cm', 'c ) 9 cm', 'd ) 9.5 cm', 'e ) none']
Example Output: c

Example Input: Problem: four horses are tethered at 4 corners of a square field of side 70 metres so that they just can not reach one another . the area left ungrazed by the horses is : 
Options: ['a ) 1050 sq . m', 'b ) 3850 sq . m', 'c ) 950 sq . m', 'd ) 1075 sq . m', 'e ) 1065 sq . m']
Example Output:
a