A. x2+y2-2x-6y=0

B. x2+y2-4x-4y=0

C. x2+y2-6x-3y=0

D. none

The limiting points of the coaxal system x^{2}+y^{2}+2λx+4=0 are

The equation of the circle passing through (2, 1) and touching the coordinate axes is

The length of the tangent from the point (-1, 1) to the circle x^{2}+y^{2}-4x+k=0 is equal to 2 then k=

The equations of the tangents to the circle x^{2}+y^{2}=16 which are inclined at an angle of 60^{0} to the x-axis is

The common chord of x^{2}+y^{2}-4x-4y=0 and x^{2}+y^{2}=16 substends at the origin an angle equal to