The set of all values of a2 for which the line x + y = 0 bisects two distinct chords drawn from a point P( 1+a /2 , 1−a /2 ) on the circle
2x² + 2y² − (1+a)x − (1−a)y= 0 is equal to
(1) (8,[infinity])
(2) (4,[infinity])
(3) (0,4)
(4) (2,12)