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

Ex Input:
Problem: 61 small identical cubes are used to form a large cube . how many more cubes are needed to add one top layer of small cube all over the surface of the large cube ? 
Options: a ) 64 , b ) 128 , c ) 152 , d ) 155 , e ) 256

Ex Output:
d


Ex Input:
Problem: the length of a rectangle is 2 times its width . if the width of the rectangle is 5 inches , what is the rectangle ' s area , in square inches ? 
Options: ['a ) 50 square inches', 'b ) 75 square inches', 'c ) 68 square inches', 'd ) 89 square inches', 'e ) 92 square inches']

Ex Output:
a


Ex Input:
Problem: there are 6 equally spaced points a , b , c , d , e and f marked on a circle with radius r . how many convex pentagons of distinctly different areas can be drawn using these points as vertices ? 
Options: ['a ) 6 p 5', 'b ) 1', 'c ) 5', 'd ) none of these', 'e ) can not be determined']

Ex Output:

d