Oxygen.
Oxygen was fatal when organisms started using photosynthesis, this event was known as the Great Oxidation Event.
Answer:
A.
Explanation:
All other options are simply situational, while cold periods are usually seasonal.
Answer:
Punnett Squares are unable to predict the offspring of an asexual organism because there is only one parent from which the offspring can receive genes from. The whole point of a Punnett Square is the fact that it covers all possible offspring outcomes besides mutations from the usual two parents.
I would say the second answers, growth. This is because we need the nutrients and vitamins from food to help us grow, and keep us healthy.
