Final answer:
The sentence requires a comma after 'woods' and a colon after 'woods:'
Step-by-step explanation:
The sentence requires a comma after 'woods' and a colon after 'woods:', so the correct punctuation is: Thoreau explains why he decided to live in the woods, "I did not wish to live what was not life, living is so dear; nor did I wish to practise resignation, unless it was quite necessary."
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