Answer:To prove a congruence of triangles using the HL (Hypotenuse-Leg) criterion, three pieces of information must be known: (1) the hypotenuse of one right triangle is equal to the hypotenuse of the other right triangle, (2) one leg of the first right triangle is equal to one leg of the second right triangle, and (3) both triangles are right triangles. In the context provided, side AC and side DF are equal in length, and both triangles have a right angle at vertices B and E respectively. Therefore, knowing these two sides are equal and that both triangles are right-angled allows us to apply the HL criterion for proving their congruence.Step-by-step explanation: