AB is a diameter of a circle with centre O. CB is a tangent to the circle at B. AC intersects the circle at G. If the radius of the circle is 6 cm and AG = 8 cm, then the length of BC is:

A

$$2\sqrt6$$ cm

B

$$6\sqrt5$$ cm

C

$$2\sqrt5$$ cm

D

$$6\sqrt6$$ cm