For designing a new tier-upgrade process in a Loyalty Program, the Consultant should select:

A flow to perform the tier-upgrade rule and another flow to perform the tier-upgrade orchestration process (C): This approach allows for the separation of concerns, where one flow is responsible for evaluating whether members meet the criteria for a tier upgrade, and another flow is responsible for the actual process of upgrading the member's tier. This modular design improves maintainability and scalability.

A data-processing-engine (DPE) to identify the qualified members (D): The DPE can efficiently process large sets of member data to identify those who qualify for a tier upgrade based on the program's criteria. This component is crucial for automating the tier-upgrade process at scale, especially in programs with a significant number of members.

Option A combines both processes into a single flow, which could become complex and harder to maintain. Option B suggests using a single flow for scheduling and processing, which might not offer the required flexibility and efficiency for handling complex tier-upgrade criteria and orchestration.

Salesforce documentation on Loyalty Management provides guidelines on leveraging Flow and DPE for automating and orchestrating various loyalty program processes, including tier upgrades.