Final answer:
The sentence that does not have a positive adverb is 'The tree caught fire when it was suddenly struck by lightning.'
Step-by-step explanation:
Out of the given options, the sentence that does NOT have a positive adverb is: The tree caught fire when it was suddenly struck by lightning. This sentence does not contain an adverb that expresses a positive or pleasant tone. It simply describes an event in a neutral manner.
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