Triangles ABC and ADC can be congruent by HL criterion, and the legs allowing the use of HL are AB and AD.
Step-by-step explanation:
Given the diagram, we can see that triangles ABC and ADC share the side AC and have a right angle at angle C. To determine if the two triangles are congruent by HL (Hypotenuse-Leg) criterion, we need to check if the hypotenuse and one leg are congruent. In this case, the hypotenuse is the side AC, and the legs are AB and AD. So, if AC = AC and AB = AD, then ΔABC ≅ ΔADC by HL.
The legs that allow the use of HL are AB and AD.