Final answer:
The appropriate word to fill in the blank in the sentence is 'succeeded'. This is the past tense form of the verb 'succeed', making it suitable for a sentence discussing a past event.
Step-by-step explanation:
The blank in the sentence 'The scientist _____(success) in their efforts to find a cure' should be filled with the word 'succeeded' to make the sentence grammatically and temporally correct. The word 'succeeded' is the past tense form of the verb 'succeed'. Here, the sentence is speaking about a past event, specifically the scientist's successful efforts to find a cure. Hence, the past tense version of the verb is most appropriate:
'The scientist succeeded in their efforts to find a cure for the disease.' This sentence now accurately communicates a completed action in the past.
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