This solution requires two distinct capabilities: a guided user interface for submission and a structured system for routing and authorization.

Flow Builder is the ideal tool for creating a guided, screen-based process (Screen Flow) that walks users through the steps of submitting an expense report. This directly addresses the need for a "guided expense report process" and simplifies submissions.

An Approval Process is the standard Salesforce feature designed specifically for managing "routing and authorizations." It automates how records are approved, defining the chain of command, criteria for approval, and the actions to be taken upon approval or rejection. A flow can initiate an approval process once the user has completed the guided submission.

A. Validation Rule: A Validation Rule is used to enforce data integrity and quality by preventing users from saving invalid data. It does not guide users through a process or manage approvals.

D. Quick Action: A Quick Action provides a shortcut to perform a specific task, such as creating a record or launching a flow. While it could be used to start the process, it does not build the guided interface or the approval logic itself.

1. Flow Builder & Screen Flows:

Salesforce Help

Flow Builder: "With Flow Builder

you can build screen flows to guide your users through a business process." This directly supports using Flow Builder for the "guided expense report process."

Salesforce Help

Flow Core Action: Submit for Approval: This document explicitly details how a Flow can be used to "Submit one or more records for approval

" confirming the synergy between Flow Builder and Approval Processes.

2. Approval Process:

Salesforce Help

Set Up an Approval Process: "An approval process automates how records are approved in Salesforce. An approval process specifies each step of approval

including who to request approval from and what to do at each point of the process." This confirms its role in handling routing and authorizations.