The answer comes from Salesforce's separation of responsibilities. Use C. A summary report on the Opportunity object. The decision turns on embedded reporting. Report chart components depend on an accessible source report and a chart-capable report format. Private reports and reports without charts cannot support the same embedded record-page experience.
This is how the same requirement would be handled in a well-governed Salesforce org: identify the controlling object, relationship, field, page, automation, or environment first, and then configure the native capability for that control point. The selected answer satisfies the requirement without requiring users to perform extra interpretation or administrators to maintain an unnecessary custom workaround.
The alternatives are plausible only if the requirement is read too narrowly. A (A tabular report on the Opportunity object) should be rejected because Reporting configuration helps analysis, but it does not enforce the requested record behavior. B (A tabular report on the Account object) would be fragile here because Reporting configuration helps analysis, but it does not enforce the requested record behavior. D (A summary report on the Account object) is only a partial match because Reporting configuration helps analysis, but it does not enforce the requested record behavior. A complete implementation should also check page assignment, field access, record ownership, and mobile behavior where those factors apply.
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