The area of a circle is Pi * R^2 (or R * R).
Since we have our radius, R, we can solve.
With our given answer choices, we do not need to multiply R by Pi, instead we will square R, as that's our only option.
4.5 x 4.5 = 20.25.
Our area is now 20.25Pi.
Your answer is C.) 20.25Pi.
I hope this helps!