Refer to the Exhibit. Switch SW2 has just been added to FastEthernet 0/23 on SW1. After a few seconds, interface Fa0/23 on SW1 is placed in the error-disabled state. SW2 is removed from port 0/23 and inserted into SW1 port Fa0/22 with the same result. What is the most likely cause of this problem?

A.
PAgP is unable to correctly negotiate VLAN trunk characteristics on the link between SW1 and SW2.

B.
BPDU filtering has been enabled either globally or on the interfaces of SW1.

C.
The spanning-tree portfast feature has been configured on SW1.

D.
The BPDU guard feature has been enabled on the FastEthernet interfaces of SW1.

E.
The FastEthernet interfaces of SW1 are unable to auto-negotiate speed and duplex with SW2.