Which event was a major source of atmospheric oxygen A. Volcanic eruptions
B. Decomposition of water
C. Outgassing
D. Photosynthesis

Please help me!

Which of these is the result of scientific research and not engineering? a. a new shoe design that features air cushioning for more comfort and protection b. the creation of glass with uv protection. c. a conclusion about diet commonalities among diabetics. d. the development of a smaller, more compact missile.

What happens to isotopes that are unstable?

As air becomes more dense, (select all that apply) o. air weighs less o. gas molecules are closer together o. air is colder o. air weighs more o. gas molecules are further apart o. air is hotter