What is route poisoning?

• A. It sends back the protocol received from a router as a poison pill, which stops the regular updates. The use of variable length subnet masks is permitted
• B. It is information received from a router that can’t be sent back to the originating router.RIPv2 supports classless routing
• C. It prevents regular update messages from reinstating a route that has just come up
• D. It describes when a router sets the metric for a downed link to infinity