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.

Example Input: Problem: it is only in the second option we find the sentence a in continuation with the opening sentence d. sentence a alone explains, why the fear has such enormous effect on the human beings.
Options: a. 28, b. 99, c. 728, d. 27, e. 271
Example Output: b

Example Input: Problem: if a mixture is 1 7 alcohol by volume and 2 7 water by volume, what is the ratio of the volume of alcohol to the volume of water in this mixture ?
Options: a. 4 / 2, b. 3 / 2, c. 1 / 2, d. 5 / 2, e. 7 / 2
Example Output: c

Example Input: Problem: obra drove 140 meters along a circular track. if the area enclosed by the circular track on which she drove is 57,600 square meters, what percentage of the circular track did obra drive ?
Options: a. 6.67 %, b. 12.5 %, c. 18.75 %, d. 29.16 %, e. 33.3 %
Example Output:
d