A variable circle is described to passes through the point (1, 0) and tangent to the curve y=tan(tan⁻¹x). The locus of the centre of the circle is a parabola whose
A. length of the latus rectum is 2√2
B. axis of symmetry has the equation x+y=1
C. vertex has the co-ordinates (3/4, 1/4)
D. none of these