The sun and the Earths core
B; As far as the relation between humans and the environment, it is obvious how much they relied on it. Not only as a food source, but for economic growth and sustainability as well. The other answers make valid points but in the context of this question, the only one that even mentions the relation is B.
Aeolian processes are effective wherever fine-grained unconsolidated sedimentary material is exposed to the atmosphere without protection
Answer:
Part of this border follows a natural boundary.
Explanation:
The answer is this one because Its a natural line between texas and Mexico and there are no mountains
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