Monique drew a square and inscribed circle on a sheet of paper, as shown below
(The picture shows a square with a circle in it and the measures are 16cm by 16cm)

Monique randomly drops a pen point-down to leave a mark on the drawing. What is the probability, expressed in percent, that the pen mark will land inside the square, but outside the circle?
A) 80.38%
B) 78.50%
C) 33.33%
D) 21.50%
Pls help me and explain how you got it.