John was explaining to Dusty that there has been extensive route flapping, which has caused extreme delay in their WAN and LAN connections. What is John referring to?

A.
Availability of routes has continually changed

B.
Routers were under attack from hackers sending UDP packets with incorrect route table updates

C.
Wormhole attacks were being carried out

D.
Several routers were going off-line for an unknown reason

Explanation:
Route flapping is a term that refers to the constant changes in the
availability of routes. If a router does not receive an update that a link has gone
down, the router will continue to forward packets to that route, which referred to
as a black hole.