What is the function of the aggregation tier in a traditional three tier Layer 2 network environment?

A.
The aggregation tier interfaces with lower tier Layer devices and provides a high-speed interconnect with
the north-bound WAN edge device.

B.
The aggregation tier relays packets between the lower tier Layer 2 devices and functions as the gateway to
the upper tier Layer 2 device.

C.
The aggregation tier provides network connectivity to end-user devices and other hosts and enforces
network access policy.

D.
The aggregation tier connects to the Internet and with lower tier Layer 2 devices to provide Layer 3 gateway
services for the network.