The set of all values of $$a^2$$ for which the line $$x + y = 0$$ bisects two distinct chords drawn from a point $$P\left(\dfrac{1+a}{2}, \dfrac{1-a}{2}\right)$$ on the circle $$2x^2 + 2y^2 - (1+a)x - (1-a)y = 0$$, is equal to:

A

$$(8, \infty)$$

B

$$(0, 4]$$

C

$$(4, \infty)$$

D

$$(2, 12]$$