Sarah described the following situation:

When fertilizer was added to one plant and nothing was added to another plant, there was a noticeable difference in the color of the leaves of the plants.

Which of the following best describes the situation?

This is an example of correlation because the fertilizer causes the plants to change color.
This is an example of causation because the application of fertilizer caused the plant to improve its leaf color.
This is an example of correlation because one plant is being fertilized and the other is not.
This is an example of causation because the leaves on both plants change color.