Answer:
This passage is mainly about asteroids striking Earth.
Explanation:
The presented passage is mostly focusing on asteroids striking Earth. It is something that has been happening since Earth has formed, and it will happen in the future as well. The vast majority of the asteroids don't really have any impact on Earth, but some have an impact that is devastating and long-lasting.
In the earlier stages of Earth, many more asteroids were falling on the surface, and the main reason for that has been the lack of atmosphere or a very thin atmosphere. As the atmosphere started to take shape and became similar to what is nowadays, the asteroid impacts decreased significantly because the atmosphere was managing to burn them and break them apart. This is not possible with all asteroids though, as some are so big and fall under an angle where the atmosphere doesn't really have any impact on them so when they fall on the surface they are able to cause sudden climatic changes, mass devastation, and mass extinction of species. Such an asteroid will be in a direction to hit Earth in the future for sure, the question remains will humans with their technology be able to prevent an impact or not.
<span>South American countries have been attempting to mirror the free market system of the United States since around 1980 (the "Washington Consensus"). This has lead to economic stagnation in these countries. In order to boost their own economies, they are now looking at the models of more productive nations whose economies are growing very rapidly and are attempting to mirror their market systems. The main countries being scrutinized are China and India, who have nationalized many of their industries/resources. This would explain the shift.</span>
The main reason for the wall's construction had always been defense. Since China's first dynasty, the empire faced a near-constant threat of attack from the nomadic tribes to the north. This included those famed Mongols as well as lesser-known groups like the Xiongnu and the Göktürks.
I believe the answer is B. I think it's B because I just studied this subject in school and it sounds best
