To determine the equation of the line that represents the reflection between the two congruent triangles in the image, we need to examine the line of symmetry.

Observing the two triangles, we see that they are mirrored across the $y$-axis. The points on the left triangle (A, B, D) correspond to points on the right triangle (H, J, G), and the reflection line appears to be the vertical line $x = 0$.

Thus, the equation of the line that reflects the two triangles is:

Answer: B. $y = 0$