Final answer:
To replace 'happily,' the adverb 'joyfully' would be the best choice.
Step-by-step explanation:
To replace the adverb 'happily' in the sentence 'Aunt Jenny was singing happily,' we need to choose an adverb that is both vivid and appropriate. The adverb 'dolefully' would not be appropriate as it means 'in a mournful or melancholy manner,' which does not match the happy tone of the sentence. On the other hand, the adverb 'joyfully' is both vivid and appropriate as it means 'in a happy or joyful manner.' Therefore, 'joyfully' is the best choice to replace 'happily.'
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