Concept:Digital tools are electronic devices or software used to create or edit designs, such as a computer, scanner, and design applications.
Explanation:A poster design requires digital tools like a computer for processing and design.
Adobe Photoshop is software used for creating and editing digital graphics.
A scanner can bring physical images into digital format for the poster.
A-4 sheets are physical paper, not digital tools.
Therefore, the set containing only digital tools is scanner, Adobe Photoshop, and a computer.
Answer:D. Scanner, Adobe Photoshop and a computer.