Final answer:
The sentence should be changed by deleting 'I thought it was' to make it more concise.
Step-by-step explanation:
The sentence should be changed by selecting option C, which is to delete 'I thought it was'. By removing this phrase, the sentence becomes more concise and eliminates the redundancy of stating both 'sucinct' and 'thought'. The revised sentence would then be:
'The article about solar energy was both succinct and relevant.'
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