Revision is the change or the revised form of something. A label displaying the depth of the drainage layer will make the diagram more helpful.
<h3>What is the drainage layer?</h3>
A drainage layer is a system that allows the flow of the water from the top external layer of the soil to the interior layer of the ground. This reduces the hydraulic gradient.
The image shown is of how to plant a container for a balcony garden and includes labeling for drainage screen, layer, and holes.
Therefore, option D. label indicating the depth of the drainage layer must be used to make the diagram more helpful.
Learn more about the diagram here:
brainly.com/question/11274664
