Implementing Cisco IP Switched Networks (SWITCH v2-0) (#266)

Refer to the exhibit. Switch 15 is configured as the root switch for VLAN 10 but not for VLAN 20. If the STP configuration is correct, what will be true about Switch 15?

All ports will be in forwarding mode.
All ports in VLAN 10 will be in forwarding mode.
All ports in VLAN 10 will be in forwarding mode and all ports in VLAN 20 will be in blocking mode.
All ports in VLAN 10 will be in forwarding mode and all ports in VLAN 20 will be in standby mode.