While troubleshooting a network outage, you discover that an employee brought a switch from home into the office to connect additional equipment to the network. In order to increase his speed, he connected this switch to both network ports in his office, resulting in a bridge loop. Which of these can you implement to prevent future occurrences of this issue?

A.
GLBP

B.
RSTP

C.
Root guard

D.
BPDU guard