The distance from the origin of the centre of three circles x2 + y2 − 2λx = c2 (where c is a constant and λ a variable) are in geometric progression. Then the lengths of the tangents drawn to them from any point on the circle x2 + y2 = c2 are also in
a) Geometric Progression.
b) Arithmetic Progression
c) Harmonic Progression
d) None of these