Which two features improve STP stability within the network design?

Refer to the exhibit.

Your company designed a network to allow server VLANs to span all access switches in a data center. In the design, Layer 3 VLAN interfaces and HSRP are configured on the aggregation switches.

Which two features improve STP stability within the network design? (Choose two.)
A . BPDU guard on access ports
B. BPDU guard on the aggregation switch downlinks toward access switches
C. root guard on the aggregation switch downlinks toward access switches
D. root guard on access ports
E. edge port on access ports
F. access switch pairs explicitly determined to be root and backup root bridges

Answer: A,E