What [fraction](https://artofproblemsolving.com/wiki/index.php/Fraction) of the large $12$ by $18$ [rectangular](https://artofproblemsolving.com/wiki/index.php/Rectangle) region is shaded?

$\text{(A)}\ \frac{1}{108} \qquad \text{(B)}\ \frac{1}{18} \qquad \text{(C)}\ \frac{1}{12} \qquad \text{(D)}\ \frac29 \qquad \text{(E)}\ \frac13$
The shaded region makes up $\frac13$ of the quarter rectangle.  The quarter rectangle is then $\frac14$ of the large rectangle, so the shaded region takes up $\frac{1}{3}\times \frac{1}{4}=\frac{1}{12}$ of the large rectangle.
$\boxed{\text{C}}$