3. As shown in the figure, $G$ is the centroid of $\triangle A B C$. From the figure, it can be deduced that there are ( ) pairs of triangles with equal area.
(A) 15
(B) 18
(C) 30
(D) 33
3. D

If any triangle (regardless of size) in the figure can be regarded as a point on a line, then the solution can be divided into the following three steps:
(1) There are six triangles with an area of $\frac{1}{2} S_{\triangle A B C}$: $\triangle A B D, \triangle A D C, \triangle A F C, \triangle B F C, \triangle C E B, \triangle A E B$, which can be considered as six points on a line. The number of pairs is $\frac{6(6-1)}{2}=15$;
(2) Similarly, there are three triangles with an area of $\frac{1}{3} S_{\triangle A B C}$, and the number of pairs is $\frac{3(3-1)}{2}=3$;
(3) Similarly, there are six triangles with an area of $\frac{1}{6} S_{\triangle A B C}$, and the number of pairs is 15.
$\therefore$ There are a total of 33 pairs of triangles with equal area.