These are the actions that can meet the requirement of restricting access to opportunities based on ownership and account association. Setting opportunity access on the role allows users to see opportunities owned by users below them in the role hierarchy, as well as opportunities associated with accounts they can access. Setting organization-wide defaults for opportunities to Private means that users can only access opportunities they own, unless they are granted access by other means, such as sharing rules or manual sharing.

To measure ROI on sales and marketing efforts by location, it is crucial to track the opportunity pipeline based on both lead source and geographic location. This approach directly ties sales outcomes (opportunities) to the sources that generated those leads, offering a clear picture of ROI across different locations.
Opportunity Pipeline as an ROI Indicator: Opportunities are directly tied to potential revenue, making them a key metric for evaluating sales success. By segmenting this data by lead source and location, Universal Containers can assess which locations are generating the most valuable sales leads.
Leveraging Opportunity Data: Salesforce enables filtering and reporting on opportunities by lead source and location, which aligns with the CEO's interest in understanding ROI geographically.
Option B (tracking accounts created) would not directly measure sales revenue, and Option C (tracking cases) is not relevant to sales and marketing ROI. For more on opportunity tracking, see Salesforce Opportunity Management documentation.