Which command on a port enters the forwarding state immediately when a PC is connected to it?

Which command on a port enters the forwarding state immediately when a PC is connected to it?
A . switch(config)#spanning-tree portfast default
B. switch(config)#spanning-tree portfast bpduguard default
C. switch(config-if)#spanning-tree portfast trunk
D. switch(config-if)#no spanning-tree portfast

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Answer: C