How does he know the lengths of AB and XY are equal?

A. AAS and then corresponding parts of congruent triangles are congruent

B. SSS and then corresponding parts of congruent triangles are congruent

C. SAS and then corresponding parts of congruent triangles are congruent

D. ASA and then corresponding parts of congruent triangles are congruent

A. AAS and then corresponding parts of congruent triangles are congruent

B. SSS and then corresponding parts of congruent triangles are congruent

C. SAS and then corresponding parts of congruent triangles are congruent

D. ASA and then corresponding parts of congruent triangles are congruent