Zoe is using the figure shown below to prove Pythagorean Theorem using triangle similarity:

In the given triangle ABC, angle A is 90° and segment AD is perpendicular to segment BC.

The figure shows triangle ABC with right angle at A and segment AD. Point D is on side BC.

Which of these could be a step to prove that BC2 = AB2 + AC2?

By distribution, AC2 plus AB2 = BC multiplied by the quantity DC plus AB.
By distribution, AC2 plus AB2 = BC multiplied by the quantity DC plus BD.
By distribution, AC2 plus AD2 = BC multiplied by the quantity DC plus AB.
By distribution, AC2 plus AD2 = BC multiplied by the quantity DC plus BD.