Answer: OPTION B.
Step-by-step explanation:
By definition, reflection is a kind of transformation in which the lengths do not change.
As you can see in the figure, the length of PR is 8 units. Then, keeping on mind the definition, when the triangle PQR was reflected across the y-axis, the triangle P'Q'R' obtained has the same lenghts as the triangle PQR.
Therefore, you can conclude that the lenght P'R' would be: 8 units.
