The business requirement is to run an automated process on a recurring schedule ("once a week") to perform an action on a set of records (count open cases for Accounts). A Schedule-Triggered Flow is the only flow type designed specifically for this purpose. It initiates automatically at a specified time and frequency, operating on a batch of records without needing a user action or a record change event to trigger it. This directly aligns with the requirement for a weekly, automated background job.

B. Record triggered flow: This flow executes only in response to a record being created, updated, or deleted, not on a predefined time-based schedule.

C. Autolaunched flow: This flow type lacks an inherent trigger and must be invoked by another process, such as Apex, a button, or another flow, not by a schedule.

D. Automation event triggered flow: This is not a standard flow type. Platform Event-triggered flows run when a platform event message is received, which is event-driven, not time-based.

1. Salesforce Help Documentation, "Flow Types":

Reference: Under the section for "Schedule-Triggered Flow," the documentation states, "Launches at a specified time and frequency for each record in a batch. This autolaunched flow runs in the background." This directly supports the use case of a weekly scheduled job.

Reference: The description for "Record-Triggered Flow" confirms it "Launches when a record is created, updated, or deleted," making it unsuitable for a scheduled task.

2. Salesforce Trailhead, "Record-Triggered Flows" Module, "Choose the Right Flow for the Job" Unit:

Reference: This unit provides a decision guide. For the question "When do you need the flow to run?", the path for "On a recurring schedule" explicitly leads to "Schedule-Triggered Flow."

3. Salesforce Help Documentation, "Schedule-Triggered Flow Considerations":

Reference: This document outlines the use case: "A schedule-triggered flow starts at a specified time and frequency for a batch of records. Configure the schedule in the Start element of your autolaunched flow. Schedule-triggered flows are ideal for jobs that require repetitive work, such as nightly reports or weekly data cleansing." This aligns perfectly with the "once a week" requirement.