Task: Question Answering
Input (English): Problem: if a is a positive integer, and if the units digit of a ^ 2 is 4 and the units digit of ( a + 1 ) ^ 2 is 1, what is the units digit of ( a + 2 ) ^ 2 ?
Options: a. 0, b. 2, c. 4, d. 6, e. 8
Output (English): a