Final answer:
When a triangle is reflected over the y-axis, the x-coordinates of its vertices change sign, while the y-coordinates remain the same. Therefore, the correct statement is option 2: A'B' = 2AB.
Step-by-step explanation:
When a triangle is reflected over the y-axis, the x-coordinates of its vertices change sign, while the y-coordinates remain the same. In this case, the vertices of triangle ABC become the vertices of triangle A'B'C'.
So, in a reflection over the y-axis, the x-coordinates of the points double in magnitude, but the y-coordinates remain the same. Therefore, the correct statement is option 2: A'B' = 2AB.