vocabulary: A. Nitrogen, B. trace gases, C. Ozone (in the upper atmosphere), D. Carbon Dioxide, E. Oxygen. fill in the blank with the letter of the term that best matches the definition 6. This gas is essential to the nutrition of plants and animals; presents in all proteins and DNA in all organisms; acts to dilute atmospheric oxygen to prevent uncontrolled combustion. 7. This gas is used by all living things; Essentials for respiration; necessary for combustion or burning. 8. plants use this oxygen; prevents some infrared heat loss from Earth's. atmosphere. 9. Neon, helium, krypton, and xenon,- don't do much. 10. This gas absorbs and scatters ultraviolet light preventing it from reaching the surface.