A circle is drawn to cut a chord of length 2a unit along x-axis and to touch the y-axis. Then the locus of the centre of the circle is-

A circle touches the x - axis and also touches the circle with centre (0,3) and radius 2. The locus of the centre of the circle is :

A circle touches the x-axis and also touches the circle with centre (0,3) and radius2. The locus of the centre of the circle is

A circle touches the x-axis and also touches the circle with centre at (0,3) and radius 2. The locus of the centre of the circle is

A variable chord of the circle x^2 + y^2 - 2 ax = 0 is drawn through the origin. Then the locus of the centre of the circle drawn on this chord as diameter is:

A circle touches the X-axis and also touches the circle with centre (0, 3) and radius 2. The locus of the centre of the circle is x^2 = 10y + k , then k = ?