Hi, Regarding the first question, neither is incorrect, but the last of the three would be most commonly used - “why are snakes the symbol of medicine?” The second one can be used too, and it would be perfectly fine. The first one however you would only use if you are speaking of a specific snake but, as you are asking why snakes in general are the medicinal symbol, you would use the second or third question. Regarding the second question, again, both are fine and correct. “The elephant is a huge animal...” can be taken to mean both a specific elephant, or elephants in general (context would inform your meaning).

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