Answer:
Trade leads to the sharing of ideas, resources and culture.
Explanation:
Trading usually happens when two civilizations need a certain resource that they do not have, and that another civilization has. Trading is the more peaceful route, in which both civilizations get something they need while giving something that they have a surplus of. Trading also generally leads to alliances and the intermingling of the two civilizations, including culture, ideas, etc.
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The first was walled cities. Another is both offensive and defensive was a fleet of warships. And a third was alliance with other cities.
Answer:
A. The Sung army had trebuchets