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Answer:
Most of the oxygen in the atmosphere is in the form of O2, which means it is made up of molecules containing two oxygen atoms. Ozone, however is O3, which means it is made up of molecules containing three oxygen atoms. O2 is what we breath, and what plants release from photosynthesis. Ozone occurs naturally high in the stratosphere, where it absorbs ultraviolet light, protecting us here on the surface from skin cancer. Ozone can also occur closer to the surface of the earth as a pollutant. It is formed from reactions with O2 and chemicals emitted from factories and cars. It comes in the form of smog.
So in general:
Oxygen (O2): Essential to human life
Ozone (O3) in the stratosphere: essential to protecting life on earth
Ozone (O3) on the surface of the earth: toxic to human life, caused by pollution
Answer:
Explanation:
Given
Total time=27 min 43.6 s=1663.6 s
total distance=10 km
Initial distance 
time taken=25 min =1500 s
initial speed 
after 8.13 km mark steve started to accelerate
speed after 60 s
distance traveled in 60 sec
time taken in last part of journey
distance traveled in this time
and total distance
