Europe's System of Military Alliances
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The answer to the question is d
An ally is a:
combine or unite a resource or commodity with (another) for mutual benefit
It helps one side more than the other, for the side with the allies has a better advantage than the side with little to no allies.
Answer: Noisy
Explanation: Urban areas are kind of like cities and you kind of just like have to find the word that fits best in that sentence.
