A secant PAB is drawn from an external point P to the circle with centre O, intersecting it at A and B. If OP = 17 cm, PA = 12 cm and PB = 22.5 cm, then the radius of the circle is:

A. $$2\sqrt 3 {\text{ cm}}$$

B. $$\sqrt {19} {\text{ cm}}$$

C. $$\sqrt {17} {\text{ cm}}$$

D. $$3\sqrt 2 {\text{ cm}}$$

Answer: Option B