Task: Question Answering
Input (English): 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 6, what is the units digit of ( a + 2 ) ^ 2 ?
Options: a. 1, b. 3, c. 5, d. 6, e. 8
Output (English): c