The Founding Fathers wanted to declare that America was an independent nation, and explain why they were declaring it.
In Aztec social hierarchy, people who are called "Serfs" are the ones expected to support the upper class. They belong to the lowest social class in the Aztec culture and required to do labors for the nobles. As for the Incas, "Commoners" (farmers, artisans, servants, etc.) are required to support the higher class for they do not practice slavery. Majority of Inca's population belongs to the commoner class.
The dust bowl and caused by dieing plants and pestisides
The correct answer to this open question is the following.
Although the question has no options, we can answer the following.
After 600 BCE, the world witnessed historical developments such as the surge of the Phoenicians in the Mediterranean Sea, a great group of sailors that built impressive ships for their time and developed the first kind of alphabet.
In that time, there were also important advancements in philosophy and religious beliefs such as the rise of Confucianism and Daoism, in China, or the influence of Zoroastrianism in the region of Persia, during the rule of the Sassadine dynasty.
Gravity exerts a downwards force on the roots.