Final answer:
In terms of the provided options, plants have the highest amount of DNA methylation because they are complex eukaryotic organisms that utilize methylation extensively in development and stress responses.
Step-by-step explanation:
When comparing different organisms in terms of DNA methylation, it's important to understand that this process refers to the addition of methyl groups to the DNA molecule, which can change the activity of a DNA segment without changing its sequence. Methylation is typically found at higher levels in organisms with complex development patterns and cellular differentiation. In the options provided plants, yeast, bacteria, and humans, it's the eukaryotic organisms (plants, yeast, and humans) that have a more complex developmental and regulatory framework, thus they would exhibit more DNA methylation compared to bacteria, which are prokaryotes.
In particular, plants are known to have extensive methylation across their genomes, which plays an essential role in their development, defense against stress, and controlling gene expression. Humans also have significant levels of DNA methylation, essential for normal development and associated with various regulatory processes. While yeast, as a eukaryote, does experience methylation, their level of complexity is lower compared to plants and humans. Considering these facts, the option with the highest amount of DNA methylation would be plants (option c).