* The recordSetVar attribute of the <apex:page> tag allows a Visualforce page to handle multiple records, which is ideal for list buttons that display a page for bulk editing.
Why not other options?
* A: Standard controllers can be extended, but using recordSetVar is the direct and best-supported method for this scenario.
* B: There is no such concept as a "Custom List Controller" in Visualforce.
* C: <spex:listButton> is not a valid Visualforce tag.
References:
* Visualforce Standard Controller with RecordSetVar