Final answer:
The catalog_manager role is responsible for updating the cart layout in a service management system, not the catalog_admin or itil_admin roles.
Step-by-step explanation:
The catalog_manager role is typically responsible for tasks related to configuring service catalogs, including updating the cart layout in a service management system. The catalog_admin and itil_admin roles generally have different responsibilities.
The catalog_admin is usually more focused on the overall service catalog management, and the itil_admin often handles incident and change management but may not have permissions to modify the cart layout. Therefore, the correct answer is D. catalog_manager.