Choice D will create an irrational number when added. This is because a rational number plus a rational number will always be irrational (you can experiment this by trying to add rational numbers to pi). For example, 3 + pi = 6.1415926..... or .
Given the function f(x) = (x + 1)^2 - 3, we recognize that because of the x^2 factor we have a parabola that opens up. Its vertex is (-1, -3), which I have swiped from the given equation. The axis of symm is x= -1.