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: kim has 3 pairs of shoes; each pair is a different color. if kim randomly selects 2 shoes without replacement from the 6 shoes, what is the probability that she will select 2 shoes of the same color ?
Options: a. 2 / 5, b. 1 / 5, c. 1 / 9, d. 1 / 10, e. 1 / 25

Ex Output:
b


Ex Input:
Problem: a train of length 250 m crosses a bridge of length 150 m in 20 seconds. what is the speed of train ?
Options: a. 33, b. 27, c. 25, d. 22, e. 72

Ex Output:
e


Ex Input:
Problem: a mobile battery in 1 hour charges to 20 percent. how much time ( in minute. will it require more to charge to 50 percent.
Options: a. 145, b. 150, c. 175, d. 160, e. 130

Ex Output:

b