<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.
Answer:
A. Global Positioning System (GPS)
Explanation:
The Global Positioning System (GPS) is the most accurate way to find your exact location, virtually anywhere on the planet, thanks for a large network of satellites orbiting the planet and providing location information. That system is also complemented by the cellular towers if you're using a cell phone.
Aerial photography is great, but it will not tell you where you are.
Remote sensing is to gather information from a distance, not relevant to the question here.
The Geographic Information Systems are information systems to give information about the land matched with precise GPS information, used in mining for example, but it's not able to tell you where you are, it's to tell where a gold deposit is however.
Answer:
Timbuktu
Explanation:
It became part of the Mali Empire early in the 14th century. In the first half of the 15th century, the Tuareg tribes took control of the city for a short period until the expanding Songhai Empire absorbed the city in 1468. A Moroccan army defeated the Songhai in 1591 and made Timbuktu, rather than Gao, their capital.
