<span> 84 billion cubic meters per year</span>
The correct answer is - cyanobacteria.
The atmospheric oxygen came from the cyanobacteria. These were one of the earliest living organisms on Earth. The cyanobacteria was using photosynthesis in order to create its own food. The photosynthesis process requires sunlight, carbon dioxide, water, and oxygen. The oxygen is mostly released as a waste product from the process of photosynthesis, thus the cyanobacteria were literally releasing oxygen that was ending up into the atmosphere. As more and more cyanobacteria there were across the planet, more and more oxygen they were releasing into the atmosphere, slowly changing the composition of the atmosphere, and setting the basis of it as we know it now.
Answer:
water it yield is 244290.45 ft
Explanation:
given data
specific storage SS = 2.4 × 
ft
thickness b = 300 ft
water declined ΔH = 4.8 ft
radius r = 1,500 ft
to find out
How much water would it yield
solution
we know that
volume of water is
Vw = S × Area × ΔH ..............1
here S = specific storage × thickness
S = 2.4 × × 300
S = 7.2 × 
and
area = πr² = π 1,500² = 7068589.471 ft²
so
volume of water is
Vw = 7.2 × × 7068589.471 × 4.8
Vw = 244290.45
so water it yield is 244290.45 ft
A radioactive element with a half-life of 1,000 years, and starting mass of 20 grams, will need 2,000 years to decrease to 5 grams.
Explanation:
The radioactive elements all have a specific half-life. Each element's half-life is well known, and they are used by scientists of numerous fields as they are excellent for determining the age of a particular item, be it or organic or non-organic nature. In this case, we have a radioactive element with a half-life of 1,000 years, and starting mass of 20 grams.
The half-life basically means that half of the mass of an element is lost during a particular period of time. For the element in question we need to find out how much time will be needed for it to decrease to 5 grams. In order to get to the result, we just need to add 1,000 years on every decrease of half of the mass:
20/2 = 10
10/2 = 5
So in 1,000 years, the element in question will decrease to 10 grams, and in further 1,000 years (2,000 cumulatively) it will decrease to 5 grams.
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