Earth's mantle plays an important role in the evolution of the crust and provides the thermal and mechanical driving forces for plate tectonics. Heat liberated by the core is transferred into the mantle where most of it (> 90%) is convected through the mantle to the base of the lithosphere.
The answer is A, Viruses
Viruses cannot reproduce on their own , so they have to inject their DNA or RNA into the nucleuus of a cell. By doing this, the virus will take over that cells and within times, that cells will pop up and producing more viruses.
This reproduced virus will repeat the same process until our immune systems stop them
3D models are better than diagrams cause a diagram is flat, and its on a piece of paper, on the other hand 3D models have 3 Dimensions which show the model in a different view, they are also sometimes on paper but you have a better view if the model which helps you get more information of the diagram.
Hope I helped ya!! And plz put it under the right subject next time. This should go under Math.