The answer is A, cause/effect. Marcia is focusing on how the war started, what ended it, and how it affected America. Cause/effect covers all these things, while the other answers either skip over these things completely or concentrate on only a few.
What are the implications of cashless society?
Benefits of a Cashless Society
Paper trails: Financial crime should also dry up. It is harder to hide income and evade taxes when there's a record of every payment you receive. Money laundering becomes much harder if the source of funds is always available. No cash management: It costs money to print bills and coins.
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