4. The diagram shows a square, its two diagonals and two line segments, each of which connects two midpoints of sides of the square.
What fraction of the area of the square is shaded?

A $\frac{1}{8}$
B $\frac{1}{10}$
C $\frac{1}{12}$
D $\frac{1}{16}$
E $\frac{1}{24}$
4. D The diagram shows that a triangle whose area is one quarter of that of the square may be divided into four congruent triangles, one of which is the shaded triangle. So the required fraction is $\frac{1}{4} \times \frac{1}{4}=\frac{1}{16}$.