Figure $ABCD$ is a square. Inside this square three smaller squares are drawn with the side lengths as labeled. The area of the shaded $L$-shaped region is

$\text{(A)}\ 7 \qquad \text{(B)}\ 10 \qquad \text{(C)}\ 12.5 \qquad \text{(D)}\ 14 \qquad \text{(E)}\ 15$
The side of the large square is $1 + 3 + 1 = 5$, so the area of the large square is $5^2 = 25$.
The area of the middle square is $3^2$, and the sum of the areas of the two smaller squares is $2 * 1^2 = 2$.
Thus, the big square minus the three smaller squares is $25 - 9 - 2 = 14$.  This is the area of the two congruent L-shaped regions.
So the area of one L-shaped region is $\frac{14}{2} = 7$, and the answer is $\boxed{A}$