The maximum speed you can achieve using Cat 6 Ethernet copper media is 10 Gbps over short distances (up to 55 meters). For longer distances (up to 100 meters), the maximum speed is 1 Gbps.
So, while 1 Gbps is certainly correct for longer cable lengths, the maximum speed achievable with Cat 6 over shorter distances is 10 Gbps. Therefore, the best answer from your options that represents the maximum potential capacity would be:
10 Gbps.