3. Divide the sides of the equilateral $\triangle A B C$ into four equal parts, as shown in Figure 1. Then the number of pairs of congruent equilateral triangles in the figure is ( ).
(A) 100
(B) 121
(C) 144
(D) 169
3. C.

Let the side length of the equilateral triangle be 4. From Figure 1, we can see:
(1) There are 16 equilateral triangles with a side length of 1, all of which are congruent, and the number of pairs is $15+14+\cdots+1=120$;
(2) There are 7 equilateral triangles with a side length of 2, all of which are congruent, and the number of pairs is $6+5+4+3+2+1=21$;
(3) There are 3 equilateral triangles with a side length of 3, and the number of pairs is $2+1=3$.
In summary, there are $120+21+3=144$ pairs of congruent triangles.