In which two locations should the Spanning Tree protocol root guard feature be implemented?

Refer to the exhibit.

A network engineer deployed an older switch with the same spanning-tree priority as the existing root, which caused a network outage.

In which two locations should the Spanning Tree protocol root guard feature be implemented? (Choose two.)
A . On the designated root switch downlinks to the access layer.
B . On all of non-root switch facing ports of the access layer
C . On the access layers root facing ports
D . On Layer 3 boundaries in the distribution layer
E . Globally on all network switches.

Answer: AB