If you want to ensure the exclusion is updated before the audience query runs, you should place the audience SQL Query Activity in a step after the exclusion SQL Query Activity. This way, the exclusion query will run first and update the data extension with the subscribers who should be excluded from the send. Then, the audience query will run and pull the subscribers who meet the criteria for the send, excluding those who were filtered out by the previous query. Placing a wait step between them or placing them in the same step will not guarantee that they will run in the correct order. You can learn more about this in the [Automation Studio Basics] module on Trailhead.

Explanation
The correct answer is A because a SQL Query activity can be used to select the unique email addresses from the data extension, a Data Extract activity can be used to export the data to a CSV file, and a File Transfer activity can be used to move the file to the Enhanced FTP Export folder. A Filter activity is not needed because the SQL Query can handle the filtering logic. A File Transfer activity is required to move the file from the Safehouse to the FTP folder.

List-Unsubscribe header is a feature that allows subscribers to unsubscribe from an email by clicking a link in their email client. This link is added by Marketing Cloud to the email header and can trigger an unsubscribe reason related to RMM, even if RMM is not enabled in the account. [Source: Trailhead]