One is definitely tourism.
Explanation:
The factor that jeopardizes the ecosystem in Eastern Europe is the tourism industry. Individuals simply travel there and have a fabulous time yet they don't pay attention and leave beaches dirty. They are not dealing with nature and the administrations can't do much since sightseers leave a lot of money for the nations.
The answer is b. a common currency
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Answer:
Explanation:
So we can use them for further research in the future
