In a Large Enterprise Network with Multiple Data Centers and Thousands

In a large enterprise network with multiple data centers and thousands of access devices, OSPF is becoming unstable due to link flapping. The current design has the access devices multihomed to large aggregation routers at each of the data centers. How would you redesign the network to improve stability?

A) Add a layer of regional Layer 3 aggregation devices, but leave the ABR function on the data center aggregation routers.
B) Add a layer of regional Layer 2 aggregation devices, but leave the ABR function on the data center aggregation routers.
C) Add a layer of regional Layer 3 aggregation devices and move the ABR function to the regional aggregation device.
D) Add a layer of regional Layer 2 aggregation devices and move the ABR function to the regional aggregation device.