Answer: C is the correct statement " In ΔADC and ΔBCD AD=BC, opposite sides of a rectangle are congruent"which completes the proof .
Step-by-step explanation:
Given: A figure shows a rectangle ABCD having diagonals AC and DB.
Anastasia wrote the proof given in picture to show that diagonals of rectangle ABCD are congruent.
We can see the Statement 2 which tells that AB=CD, opposite sides of a rectangle are congruent. In Statement 3 she used Pythagoras theorem to show AC²= BD² by using Statement 1 and 2.
Thus we can see she need to introduce two triangles named as ACD and BCD and the remaining sides to write the proof is AD=BC with correct reason i.e. opposite sides of a rectangle are congruent.
Therefore Statement 1 would be In ΔADC and ΔBCD AD=BC, opposite sides of a rectangle are congruent.
