Answer:- D) AAS Theorem
Explanation:-
Given :- Δ ADC where ∠A=∠C , ∠ABD=90° which means Bd is an altitude .
⇒∠CBD =90° [∵∠ABD+∠CBD=180° linear pair]
Proof :- In ∆ABD and ∆CBD.
∠A=∠C [given]..> angle
∠ABD=∠CBD [right angle]..> angle
BD=BD [Reflexive property]..> side
⇒ ∆ABD ≅ ∆CBD [by AAS congruence theorem]
AAS congruence theorem tells that if two angles and one side of a triangle is congruent to the two angles and one side of a triangle then the triangles are congruent.