Correct Answer: 3 cm

Explanation:

let. the tangent AB = 5cmDistance at the point A from the center the circle OA = 4cm

Now drawing a perpendicular from the tangent on the center of the circle OB. we get a right angled triangle $\Delta$AOB

Applying Pythagorean theorem

OA$^{2}$+OB$^{2}$= AB$^{2}$

=> 4$^{2}$+OB$^{2}$=5$^{2}$

=> OB$^{2}$= 25-16

=> OB$^{2}$ = 9 =3$^{2}$

So, OB = 3

The radius of the circle is 3cm.