What is the effect of entering the switchport mode access configuration command on a switch?

The effect of entering the switchport mode access configuration command on a switch is that it sets the specified interface to permanently operate as an access port, which is used to connect end devices such as computers and printers to the switch. This command does the following:

• It disables DTP (Dynamic Trunking Protocol) on that interface. DTP is used on switch interfaces to negotiate if the port should become a trunk, but setting the port to access mode manually disables DTP because the port is no longer eligible to form a trunk, as it is explicitly designated for access mode.

Therefore, the correct statement is:

• It disables DTP on a non-trunking interface.

The command does not disable an unused port, manually enable a trunk link, or enable BPDU guard on a specific port. Those would be the effects of different commands.