Answer:
Disease and Famine
Explanation:
If there is a disease that affects a type of plant, having other types of crops to rely on could save one from starvation. Also, only planting one crop in an area can change the pH and nitrogen levels in negative ways, so that eventually no plants can grow there. Not to mention the obvious balanced diet needed for a healthy body.
Answer: Earth spins on its axis
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Fossil fuels and green house gases which burn holes in the ozone layer of the atmosphere causing global warming
