<u>Answer:
</u>
The build-up of three oxygen created our ozone layer around two billion years ago.
<u>Explanation:
</u>
- 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.
Your answer would be, Letter (A), <span>Endemic diseases can result in decreasing population numbers: many people die from diseases, and others move away from or avoid moving to places where diseases are rampant.
Hope that helps!!!
</span>
Weather is the day-to-day state of the atmosphere in a region and its short-term (minutes to weeks) variations, whereas climate is defined as statistical weather information that describes the variation of weather at a given place for a specified interval.
