In this task, you need to provide the correct option for a given problem from the provided options.

Input: Consider Input: Problem: a bag holds 3 red marbles and 3 green marbles . if you removed two randomly selected marbles from the bag , without replacement , what is the probability that both would be green ? 
Options: a ) 1 / 10 , b ) 1 / 6 , c ) 3 / 10 , d ) 1 / 5 , e ) 1 / 2

Output: d


Input: Consider Input: Problem: what is the greatest value of x such that 4 ^ x is a factor of 21 ! ? 
Options: a ) 5 , b ) 6 , c ) 3 , d ) 2 , e ) 4

Output: b


Input: Consider Input: Problem: what is the square root of 239,121 ? 
Options: a ) 476 , b ) 489 , c ) 497 , d ) 511 , e ) 524


Output: b