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 greatest number which leaves the same remainder when it divides 16, 46 and 82.
Options: a. 18, b. 8, c. 12, d. 16, e. none of these

Ex Output:
e


Ex Input:
Problem: a cyclist bikes x distance at 10 miles per hour and returns over the same path at 9 miles per hour. what is the cyclist ' s average rate for the round trip in miles per hour ?
Options: a. 8.1, b. 8.3, c. 8.6, d. 8.9, e. 9.5

Ex Output:

e