Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.

Ex Input:
Problem: in a certain pond, 50 fish were caught, tagged, and returned to the pond. a few days later, 50 fish were caught again, of which 5 were found to have been tagged. if the percent of tagged fish in the second catch approximates the percent of tagged fish in the pond, what is the approximate number of fish in the pond ?
Options: a. 400, b. 500, c. 1,250, d. 2,500, e. 10,000

Ex Output:
b


Ex Input:
Problem: find the value o f 72519 x 9999 = m ?
Options: a. 434539873, b. 355797990, c. 435453490, d. m = 725117481, e. 873430134

Ex Output:
d


Ex Input:
Problem: a number is said to be prime saturated if the product of all the different positive prime factors of z is less than the square root of z. what is the greatest two digit prime saturated integer ?
Options: a. 99, b. 98, c. 97, d. 96, e. 95

Ex Output:

d