Correct answer is D.
Look at the unit digit of a number, and ignore the other digits. We will denote other digits with dots (......). Let's say we have a number .....3.
......3^2 - 3 = ......9 - 3 = ........6
Check for numbers which unit digit is 1,2,4,5,6,7,8,or 9. They don't satisfy any of the answer options.
