The diameter of the circle is = 100 because is the running track itself. However, as you can see from the figure the diameter is also one side of the square.

So, one side of the square is 100 and the area is \(s^2 = 100^2 = 10,000\)

The radius is \(= \pi r^2 = \pi 50^2 = 3.14 * 2,500 \approxeq 7,850\). This is the area of the circle.

Therefore, the area of the circle enclosed into the square is the follow

\(7850 \approxeq \frac{3}{4} of 10,000\).

D is the answer