According to the exam guide, one of the objectives is to "describe best practices for implementing a single-org strategy in a B2C scenario"1. This implies that option D is the best practice for loading individual consumers as contacts in Salesforce. This approach avoids creating unnecessary accounts and reduces data duplication. Option C is not correct because it creates one account per contact, which increases data volume and complexity. Options A and B are not correct because they do not leverage the standard contact object, which provides native functionality and integration with other Salesforce features.

Determining if any integration points create records in Salesforce, running key reports to determine what fields should be required, and reviewing the sharing model to determine impact on duplicate records are three areas of Salesforce that the architect should review before proposing any design recommendation. These areas will help to identify the sources and quality of data, the business rules and validations for data entry, and the access and visibility of data across users and roles. Reviewing the metadata xml files for redundant fields to consolidate, and exporting the setup audit trail to review what fields are being used are not necessary steps for optimizing a data stewardship engagement, as they are more related to metadata management and audit tracking.

Using Bulk API to export 1 million records from Salesforce is the best option. Bulk API is a RESTful API that allows you to perform asynchronous operations on large sets of data. You can use Bulk API to create, update, delete, or query millions of records in batches. Bulk API is optimized for performance and scalability, and it can handle complex data loading scenarios.