Final answer:
The process described is known as vendor management, where the project manager manages the relationship with the service provider to ensure the project's needs are met.
Step-by-step explanation:
When a project manager researches and sources a specific service and then has to manage that relationship, this activity is referred to as vendor management. This involves overseeing and controlling every aspect of the relationship with the service provider or supplier, ensuring that the contractual obligations are met and that the service delivery is aligned with the project's needs. The correct answer to your question would be (d) Vendor Management.