B. Process builder

Explanation:
To automate an outbound message for the sales team at Ursa Major Solar, the administrator should use Process Builder.

Process Builder is a powerful automation tool that allows administrators to define a set of criteria and associated actions to be executed when the criteria are met. In this case, the criteria could be set to trigger the outbound message when a specific event or condition occurs, such as a new opportunity being created.

Flow Builder is another automation tool that allows administrators to build and automate complex business processes. However, for a simple outbound message automation task, Process Builder would be the recommended option.

Workflow Rules are used to automate standard internal procedures and processes to save time across your org. However, it does not support outbound message actions.

Task Assignment is used to assign tasks to specific users or queues based on specific criteria, it does not support outbound message actions....

I think C is correct - 'outbound message' is only possible on 'workflow rule'

A is the correct answer. C is possible however, rather prioritise using a Flow.