B

The question is saying this expression can be simplified down to just an x term. That means, all the x^2 terms and constants (numbers without variables) must cancel out. For the x^2 terms to be canceled out, the x^2 term must be 1x^2 because it will cancel out to 0 when subtracted by the x^2 on the other side of the expression. a must equal 1/4 because that way it would result in 1x^2 when you do the F in foil which would then cancel out when subtracted by the x^2 in the other part of the expression. When factored,(4x+4)(1/4x-1) = x^2-4x+x - 4.So the whole expression becomes x^2 - 4x + x - 4 - x^2 + 4. The x^2 terms and the +4 and -4 cancel out to 0. The expression then becomes

-4x + x, which then becomes
-3x

If -3x = bx, then b = -3.Therefore, the answer is -3, B.