This is a personification. An idiom would be something like a proverb while hyperbole would be exaggeration. A metaphor is when there's a meaning that's implied. Personification is when you give objects that don't behave like people, human traits. The raven in reality probably doesn't say anything, just croaks or whatever, but in the poem he keeps saying it because it's a poem.
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Answer: Merchants from different places exchange one type of coin to another.
Explanation: Moneychangers were in (virtually) every city's harbor. Traders from foreigns country came to moneychangers to change their money to the local currency (AKA local coin) so that the traders could do buisness in that country
A. Food. They fave out food surpluses that helped to lead to population growth and trade.
pollution, public education, harder to get a job