Environmental protection is the third pillar and to many, the primary concern of the future of humanity. It defines how we should study and protect ecosystems, air quality, integrity and sustainability of our resources and focusing on the elements that place stress on the environment
<u>Answer:
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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.
Answer: 
Explanation:
The Tropic of Cancer is one of the parallels (imaginary line around the Earth parallel to the equator) located in the northern hemisphere (currently its latitude is 
).
It is called "Cancer" because a long time ago, when the summer solstice occurred in the northern hemisphere (on June 20th or 21st), the Sun was in the constellation Cancer (the crab).
Now, if we were just in the North Pole, Polaris would by exactly over our heads (
over the horizon), but as we go south and find the Tropic of Cancer parallel, Polaris altitude will be approximately at an angle of over the horizon.
Hence, the altitude of Polaris measured by an observer at the Tropic of Cancer is .
Answer:
d
Explanation:
baka lang nmn po.........
