<u>Answer:
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The build-up of three oxygen created our ozone layer around two billion years ago.
<u>Explanation:
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- The ozone layer is a part of the stratosphere which is located right after the troposphere in the atmosphere of the Earth.
- The ozone gas is made up of the abundance of three oxygen molecules combining with the ultraviolet radiation emitted by the Sun.
- The development of the ozone layer happened around two billion years ago when the oxygen concentration levels on the planet began to rise slowly and gradually.
The answers are:
- air pollution; the bigger cities create lots of dust, there's always new building sites that contribute to dust and some of the working materials to pollute the air. Also there's big amount of vehicles that release toxic gases, as well as the industry.
- housing shortages; the more people there are at some city, the more difficult it is to have space for everyone, because usually the process of building new homes doesn't correspond with the amount of people coming in.
- overcrowding; the larger the population at some place, the more crowded it gets, be it in traffic, walking, in stores, institutions...
- water pollution; more people means more pollutants in the water they are using, which in return creates water shortages because big portion of the water can not be used afterwards.
- water shortages; the amount of fresh water is limited, so once the population surpases the optimal number problems with fresh water start to occur. To this also contributes the irresponsible usage of water.
Farmers supply 41% of the world's corn.
Answer: 41%
Italy's northern boundary is covered with mountain ranges, one of them, the Apennine Mountains, runs the length of the peninsula.
in 1950 there were 4.7 million people if thats' what your looking for
