5. In the right figure, $ABCD$ is a parallelogram, $M$ is the midpoint of $DC$, $E$ and $F$ are points on $AB$ and $AD$ respectively, and $EF$ is parallel to $BD$. If the area of triangle $MDF$ is 5 square centimeters, then the area of triangle $CEB$ is ( ) square centimeters.
A. 5
B. 10
C. 15
D. 20
Analysis: Area problem, Trapezoidal butterfly wings
As shown in the figure: Connect $F C, D E, F B$, in trapezoid $F B C D$, we have $S \triangle F D B=S \triangle F D C$,
in trapezoid $E B C D$, we have $S \triangle E D B=S \triangle E B C$,
in trapezoid $F E B D$, we have $S \triangle F D B=S \triangle E D B$,
so $S \triangle F D C=S \triangle E B C$, since $M$ is the midpoint of $D C$, thus $S \triangle E B C=2 \times 5=10 \mathrm{~cm}^{2}$. The answer is $B$.