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: if the area of a circle is 16 pi square feet , find its circumference .
Options: a ) 8 pi feet , b ) 28 pi feet , c ) 38 pi feet , d ) 48 pi feet , e ) 58 pi feet

Ex Output:
a

Ex Input:
Problem: the diameter of a cylindrical tin is 10 cm and height is 5 cm . find the volume of the cylinder ?
Options: a ) 125 , b ) 155 , c ) 130 , d ) 120 , e ) 100

Ex Output:
a

Ex Input:
Problem: a circular well with a diameter of 2 metres , is dug to a depth of 10 metres . what is the volume of the earth dug out ?
Options: a ) 32 m 3 , b ) 31.4 m 3 , c ) 40 m 3 , d ) 44 m 3 , e ) none

Ex Output:
b