Default routing—This is the default routing model that Prisma Access uses. Use this routing mode if you want Prisma Access to use BGP best path-selection mechanisms without adjusting any of the BGP attributes. In this mode, Prisma Access will honor any attribute advertised by the customer premises equipment (CPE). https://docs.paloaltonetworks.com/prisma/prisma-access/prisma-access-panorama-admin/prisma-access-advanced-deployments/service-connection-advanced-deployments/route-preferences-for-service-connection-traffic

in default routing, basic bgp is configured. In hot potatoe routing, a summary is sent to Prisma Access, and Prisma Access AS-PATH prepends to influence routing.

C, because of "The administrator needs to minimize the BGP configuration and management overhead on on-prem network devices." For Prisma Access we have the options for default routing and hot potato routing. Default: Use this routing mode if you want Prisma Access to use BGP best path-selection mechanisms without adjusting any of the BGP attributes. In this mode, Prisma Access will honor any attribute advertised by the customer premises equipment (CPE). Hot Potato: Use this routing method if you want your organization’s network to perform the majority of routing decisions. Hot Potato would violate the requirement of minimizing BGP configuration and management overhead.

Cannot be C as default routing would imply one connection to Prisma. The question states there are three service connections so default routing would not make sense in this scenario.

By summarizing BGP routes before advertising them, the administrator can reduce the number of individual routes that need to be advertised, which simplifies BGP configuration and management on the on-premises network devices. This approach can help streamline routing updates and improve overall network efficiency.

we need to minimize BGP config on on-prem devices so hot potato does that.

Pretty sure it is Default Routing (C) as per below: You can choose from the following routing modes with Prisma Access: Default routing—This is the default routing model that Prisma Access uses. Use this routing mode if you want Prisma Access to use BGP best path-selection mechanisms without adjusting any of the BGP attributes. In this mode, Prisma Access will honor any attribute advertised by the customer premises equipment (CPE). Hot Potato routing—Prisma Access hands off the traffic as quickly as it can to your organization’s network.

Hot potato is correct. The prepending mechanism in hot potato routing ensures symmetric routing to Prisma without any changes to the CPE BGP configuration in case of SC failure, route aggregation, and/or routing to a peered AS w/o a SC to Prisma.

https://docs.paloaltonetworks.com/prisma/prisma-access/prisma-access-panorama-admin/prisma-access-advanced-deployments/service-connection-advanced-deployments/route-preferences-for-service-connection-traffic

C minimum config on CPE, GBD35055 and mizuno92 have given right explanations

Default routing - C

I believe the answer is C. Hot Potato routing—Prisma Access hands off the traffic as quickly as it can to your organization’s network. Use this routing method if you want your organization’s network to perform the majority of routing decisions. The goal was to eliminate as much CPE configuration as possible.