Answer:
C.
crust, mantle, outer core, inner core
Explanation:
Earth is mostly made of rock.
Answer:
there were very good resources
Explanation:
Religious and ethnical problems.
It was one of the largest empires of the world with many different ethnicities. The problem was to unite people under one rule.
Another problem was communication. It was hard to transfer knowledge and news to all parts of the empire because it was too large.
