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:
The population of Africa has several specific characteristics:
- Very young: the population of Africa is very young, the median age in Africa is 19 years. For comparison, the median age in Europe is 43 years.
- High fertility: the average African woman has over 4 children, while the average European woman has 1 child or less.
- Very high population growth: because of the young population and the high fertility rate, the African population is growing very fast. Africa is projected to have over 4 billion people by the year 2100, currently, it sits at 1.3 billion people.
- Low life expectancy: the life expectancy in Africa has been improving, but it still low when compared to other parts of the world, sitting at around 60 years. For comparison, Japan, the country with the highest life expectancy on Earth, has a life expectancy of 84 years.
Answer: D. They are affordable for everyone to install.
Explanation: I hope this helps :)
Outer core.
The densest layer is the inner core but it is not given as an option. The outer core is closet to the inner core, therefore it is the correct option.