Which two options are two advantages of summarizing networks at the aggregation layer rather than at the core?

Which two options are two advantages of summarizing networks at the aggregation layer rather
than at the core? (Choose two.)

A.
It prevents the core from having unnecessary routes.

B.
It no longer needs a core layer.

C.
It prevents black hole routing.

D.
It avoids network-wide impact upon VLAN changes local to the aggregation devices.