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 Q]: 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 A]: b

[EX Q]: Problem: if a ' s height is 40 % less than that of b, how much percent b ' s height is more than that of a ?
Options: a. 66.66 %, b. 66.68 %, c. 66.766 %, d. 86.66 %, e. 66.65 %
[EX A]: a

[EX Q]: Problem: a swimmer can swim in still water at 4 km / h. if the speed of the water current is 1 km / h, how many hours will the swimmer take to swim against the current for 6 km ?
Options: a. 1.2, b. 1.4, c. 1.6, d. 1.8, e. 2
[EX A]:
e