The correct formula to find the area of a circle when given the radius \( r \) is:
\[ A = \pi r^2 \]
However, from the options you've provided, none of them match the standard formula for the area of a circle. If the letter "x" in your options represents \( \pi \) (which is approximately 3.14), then \( A = xr^2 \) could be considered the closest option, but traditionally we denote the area as \( A = \pi r^2 \).
So, if you're looking to match your answer to the closest option, pick:
A = xr^2 (assuming \( x \) is representative of \( \pi \)).