In Spanning Tree Protocol (STP), the Root Port is the port on a non-root bridge with the lowest path cost to the root bridge. This port is used for forwarding traffic towards the root bridge. The Designated Port is assigned on a network segment and is used to forward packets on that segment. The Alternate Port provides an alternative path towards the root, similar to the root port, but is blocking to prevent loops until needed. The Backup Port provides redundancy to a designated port on the same segment. Thus, the best answer is the Root Port because it specifically serves as the primary forwarding path to the root bridge.