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: what is the measure of the angle e made by the diagonals of the any adjacent sides of a cube . 
Options: ['a ) 30', 'b ) 45', 'c ) 60', 'd ) 75', 'e ) 90']
Example Output: c

Example Input: Problem: a circle and a rectangle have the same perimeter . the sides of the rectangle are 18 cm and 26 cm . what is the area of the circle ? 
Options: ['a ) 88 cm 2', 'b ) 154 cm 2', 'c ) 1250 cm 2', 'd ) 616 cm 2', 'e ) none of these']
Example Output: d

Example Input: Problem: calculate the area of a triangle , if the sides are 13 cm , 12 cm and 5 cm , what is its area ? 
Options: ['a ) 36 cm 2', 'b ) 35 cm 2', 'c ) 30 cm 2', 'd ) 32 cm 2', 'e ) 31 cm 2']
Example Output:
c