Options: 1. emissions. 2. earthquakes. 3. oxidation reaction. 4. ozone depletion. 5. global warming. 6. important habitats. 7. fairies. 8. the ozone layer strengthening.
Given those answer options, answer the question: Fact 1: Ozone depletion results in higher levels of UV radiation reaching Earth. Fact 2: Birds live on Earth, trees live on Earth. Given the two facts above, what results in higher levels of uv radiation reaching the place birds and trees live?
A:
4.