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.

Problem: find the value of 1 / ( 3 + 1 / ( 3 + 1 / ( 3 - 1 / 3 ) ) )
Options: a. 21 / 29, b. 27 / 89, c. 89 / 21, d. 29 / 21, e. none
b

Problem: what number must be added to 6, 16 and 8 to get an average of 13 ?
Options: a. 23, b. 22, c. 44, d. 33, e. 55
b

Problem: if a is a positive integer, and if the units digit of a ^ 2 is 9 and the units digit of ( a + 1 ) ^ 2 is 4, what is the units u digit of ( a + 2 ) ^ 2 ?
Options: a. 1, b. 3, c. 5, d. 6, e. c. 14

a