The correct answer is: C. Placeholders
Placeholders are the boxes on a slide that hold text, images, and other objects. They are used to organize the content of a slide and to make it easier to add and remove elements.
Design plates are a type of template that includes pre-formatted slides with placeholder text and images. They can be used to create a consistent look and feel for a presentation.
Templates are a type of document that includes pre-formatted text, images, and other elements. They can be used to create new documents quickly and easily.
Blueprints are a type of technical drawing that shows the layout and design of a building or other structure. They are used by architects and engineers to plan and construct buildings.
In conclusion, placeholders are the boxes on a slide that hold text, images, and other objects. They are used to organize the content of a slide and to make it easier to add and remove elements.