Choose 1 option.

Option C is correct because Medical Insight upvotes are handled through the UserReaction object and related out-of-the-box logic. Salesforce’s Life Sciences Cloud Developer Guide states that UserReaction represents a user’s reaction to a medical insight, such as an upvote or downvote, and that these reactions are used to identify trending insights. This directly supports the scenario because the problem involves duplicate upvotes and the inability to see total upvote counts on Medical Insight records.

Salesforce’s MedicalInsight object documentation also references fields related to ranking and upvotes, including a default rank determined based on linked insights and their upvotes. This confirms that upvote behavior is part of the standard Medical Insights data model rather than something that should be rebuilt manually.

Option A is not the best answer because MedicalInsightValidationHandler sounds focused on validating Medical Insight records generally, not specifically managing user reactions, duplicate reactions, or upvote counts. Option B is also not preferred because custom validation rules and a new roll-up summary field would duplicate behavior that Salesforce provides through the Medical Insights user-reaction framework. The requirement asks for the out-of-the-box configuration, so the consultant should activate the UserReactionMedicalInsightHandler to manage upvote reactions consistently and support the total-count behavior.

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