D, winter.... summer.
In the northern and southern hemispheres, seasons are opposite from one another. Summer would be opposite to winter. Since both A and C list the seasons as staying the same and B lists spring as opposite to winter... D is the correct answer.
1- Maize Mixed Farming System
2- Irrigated Farming System
3- Rice Tree Crop Farming System
<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.
