<image>A large square is divided into smaller squares, as shown. A shaded circle is inscribed inside each of the smaller squares. What proportion of the area of the large square is shaded?
A. $\frac{8 \pi}{9}$
B. $\frac{13 \pi}{16}$
C. $\frac{3}{\pi}$
D. $\frac{3}{4}$
E. $\frac{\pi}{4}$