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 smallest positive integer x , such that 7000 x is a perfect cube ? 
Options: a ) 4 , b ) 6 , c ) 8 , d ) 12 , e ) 18
Example Output: d

Example Input: Problem: in the xy - plane , a triangle has vertices ( 0,0 ) , ( 4,0 ) and ( 4,7 ) . if a point ( a , b ) is selected at random from the triangular region , what is the probability that a - b > 0 ? 
Options: a ) 4 / 7 , b ) 2 / 3 , c ) 3 / 5 , d ) 3 / 7 , e ) 1 / 2
Example Output: a

Example Input: Problem: the pressure someone experiences as he or she dives deeper and deeper in the ocean increases linearly . on the surface , the pressure is close to 15 pounds per square inch . 33 feet below the surface , the pressure is 30 pounds . if 25000 pounds per sq inch can crush your bones , what depth is extremely dangerous for humans ? 
Options: ['a ) 55522 feet', 'b ) 45522 feet', 'c ) 35522 feet', 'd ) 25522 feet', 'e ) none']
Example Output:
a