1. Weblink: http: /en. wikipedia. org/wiki/Fossil_fuel.
2. Weblink: http: /en. wikipedia. org/wiki/Mutation.
3. Weblink: http: /en. wikipedia. org/wiki/Cosmic_ray.
4. Weblink: http: /en. wikipedia. org/wiki/Alpha_particle.
5. Weblink: http: /en. wikipedia. org/wiki/Radiation_protection.