Assuming no further errors occur after the Try scope, the payload set to "Success - main flow" will be the final payload, and that is what will be returned to the client. So, the response message returned to a client request to the main flow's HTTP Listener, after the Validation component in the Try scope throws an error and no further errors occur, will be: C. “Success – main flow”

Not sure if it wouldn't bubble up to the main flow error handling. If not then C is correct; https://blogs.mulesoft.com/dev-guides/how-to-tutorials/mule4-error-handling-use-cases/

Because the handler inside try scope is "On Error Continue" so will return the message from the last payload