The mass extinctions that occurred 250 million years ago and 65 million years ago may have been due to gradual process or Catastrophic events.
Carbon dioxide :)
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Answer:A radical (often, but unnecessarily called a free radical) is an atom or group of atoms that have one or more unpaired electrons. ... A prominent feature of radicals is that they have extremely high chemical reactivity, which explains not only their normal biological activities, but how they inflict damage on cells.
Explanation:CAN I GET BRAINLIEST PLZZZZZZZZZZZ
The sun is a source of energy for all living things.
