The correct answer is - B. Nationalism created ethnic tensions, resulting in civil war.
The nationalism in the early 20th century turned into a very dangerous weapon used by the politicians to control the people in accordance to their interests.
Through the usage of nationalism, the leaders of the countries managed to make the people feel as something special, as superior, as the best nation in the world, and in the same time promote hatred, despise, and putting blame on other ethnic groups for their troubles. Unfortunately, that mindset was what led to a terrible bloody war.
The Earth is a "closed system" which means that the amount of rocks, carbon, metals, nitrogen, water and oxygen on earth remains constant.
So it is essential that "biogeochemical cycles renew these materials" as they move through the Earth's subsystems.
<u>Explanation</u>:
The Earth's only source of extra-planetary energy is the Solar radiations received by Earth.
The biogeochemical cycles on the planet are responsible for processing the same old rocks, metals, carbon, nitrogen, oxygen, water, and other abiotic substances on Earth in order to naturally renew them and make them available for reuse.
No naturally occurring element on Earth is newly produced. It is only renewed through biogeochemical processes.
