What allows composites (such as carbon-fiber-reinforced polymers) to be so strong and elastic? select all that apply.
- high kinetic energy of the molecules
- extensive cross-linking between molecules
- size of polymer molecule
- properties of metals and plastics

I think there would be two correct answers from the choices listed above. These are the second and the last option. Composites are strong and elastic because of the extensive cross-linking between molecules and the properties of metals and plastics. Hope this answers the question.

Yes you are correct use the scientific method