Valentina is employed under the network management team at Iris Global Services, which is a software management firm. Following a recent hacking attempt at its office, the network administrator wants her to cross$-$check whether security precautions have been enabled on the STP interfaces so that the information transmitted by the BPDUs can be protected. On inspection, she discovers that the security precautions have not been configured. Analyze what Valentina should do in order to prevent a rogue switch or computer connected to one of these ports from hijacking the network's STP paths.

a$.$

Use a BPDU guard to block BPDUs

b$.$

Use a root guard on the switches

c$.$

Use the shutdown command to disable unused ports

d$.$

Use a BPDU filter to disable STPs