In Adobe Real-Time CDP, transactional data such as orders and their associated line items are best represented using the XDM ExperienceEvent class. Unlike traditional RDBMS structures that require separate tables for headers and details joined by a foreign key, XDM is optimized for a denormalized, hierarchical NoSQL model.

For this retail use case, the architect should create a single XDM ExperienceEvent schema. The 'Order' attributes (Order ID, Date, Status, Addresses) form the base of the event, while the 'Order Items' are typically modeled as an array of objects within that same schema. This approach allows the platform to capture the entire transaction as a single 'point-in-time' event. By marking the Customer ID as an Identity, the platform's Identity Service automatically links these transactional events to the correct Real-Time Customer Profile.

Option B is incorrect because Order data is behavioral and immutable (events), whereas the Individual Profile class is reserved for stateful, slow-changing customer attributes. Options C and D are incorrect because they suggest creating multiple schemas or custom schemas to replicate the relational model. Using multiple schemas for a single transaction would necessitate complex joins, which defeats the performance benefits of the Adobe Experience Platform's NoSQL architecture. By using a single ExperienceEvent schema, the company achieves maximum scalability and ensures that the data is immediately available for high-performance segmentation and real-time activation.