Final answer:
Selah is using a hierarchical organization system to organize her computer folders, placing them in a nested structure from the most general 'Budget' folder to the more specific '2021' then 'Work' folders.
Step-by-step explanation:
Selah is using a hierarchical method of organization for her computer files by creating nested folders. Starting with the broadest category, she has created a 'Budget' folder. Within the 'Budget' folder, she has placed a more specific '2021' folder that pertains only to that year's materials.
Lastly, within the '2021' folder, she adds a 'Work' folder for even more specialized content. This is a common way to structure data so that it's easier to manage and locate specific documents when needed.