# The locus of point of intersection of perpendicular tangents to the circle $x^2+y^2=a^2$ is:
( A ) $x^2+y^2=8a^2$
( B ) $x^2 + y^2 = 4a^2$
( C ) $x^2 + y^2 = 2a^2$
( D ) $x^2+y^2=6a^2$