The equation of a circle C1 is x2+y2=4. The locus of the intersection of orthogonal tangents to the circle is the curve C2 and the locus of the intersection of perpendicular tangents to the curve C2 is the curve C3. Then,
a. C3 is a circle
b. the area enclosed by the curve C3 is 8π
c. C2 and C3 are circles with the same centre
d. None of the above