B (Separate priority queues): Both VoIP and the custom stock-trading application require low latency and jitter guarantees but serve different business functions. Best practice is to place them in separate priority queues to prevent one application's bursts from affecting the other, ensuring deterministic service levels for both mission-critical services.

Other options explained:

A: Sharing queues may lead to competition between traffic types, risking SLA violations.

C/D: CBWFQ is not sufficient for true low-latency guarantees; priority queuing is required.

—