A multi-brand company uses B2C Commerce, Service Cloud, and Marketing Cloud and wants to deliver...

Option B is correct because Marketing Cloud should implement a second business unit and provide each B2C Commerce storefront with its own Marketing Cloud business unit. This is a recommended practice to enable multi-brand marketing campaigns and segmentation based on different storefronts and customer profiles.

Option C is correct because Marketing Cloud must undergo a subscriber key migration with Salesforce Professional Services and select a subscriber key that aligns with Salesforce multi-cloud architecture best practices. This is a recommended practice to enable data integration and identity resolution across multiple Salesforce clouds using Customer 360 Data Manager. Email address is not a suitable subscriber key for multi-cloud scenarios, as it may change over time or be shared by multiple customers.

Option A is incorrect because Marketing Cloud should not serve as the Salesforce primary for customer profiles and leverage customer email addresses as a multi-cloud customer identifier. This is not a recommended practice, as it would create data quality issues, security risks, and integration challenges across multiple Salesforce clouds. Customer email addresses are also not suitable as a multi-cloud customer identifier, as they may change over time or be shared by multiple customers.

Option D is incorrect because B2C Commerce should not integrate with Marketing Cloud and create a Marketing Cloud Contact when a B2C Commerce customer registers or places an order via the storefront. This is not a recommended practice, as it would create data duplication, synchronization issues, and performance impacts across multiple Salesforce clouds. B2C Commerce should integrate with Service Cloud or Customer 360 Data Manager to create or update customer records based on their actions on the storefront.

References:

[Get Started with B2C Solution Architect Cert Prep - Trailhead]

[Certification - B2C Solution Architect - Trailhead]

[B2C Solution Architect Certification Guide | Salesforce Ben]