Why do we, as individuals, not produce all our own goods and services? a) we prefer things made by others. b) in order to eliminate scarcity. c) by specializing and trading, we all have more. d) individuals are too lazy to produce everything they need.

D is the answer. 
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C. Specializing and trading allows more variation in the market and that way we spend less time learning, but instead just exchange our skills/money gained from those skills for other goods and services and use that time for more efficient things.

While D is probably true to most people, C makes more sense/is the more appropriate answer.