Which statement about data center access layer design modes is correct？（）

A、 The access layer is the first oversubscription point in a data center design.

B、 When using a Layer 2 loop-free design， VLANs are extended into the aggregation layer.

C、 When using a Layer 2 looped design， VLANs are not extended into the aggregation layer.

D、 When using a Layer 3 design， stateful services requiring Layer 2 connectivity are provisionedfrom the aggregation layer.

E、 The data center access layer provides the physical-level connections to the server resourcesand only operates at Layer 3.