Final answer:
The data field in an Ethernet frame must be at least 46 bytes long.
Step-by-step explanation:
The data field in an Ethernet frame must be at least 46 bytes long. This is the minimum size required by the Ethernet standard and ensures that the frame has enough space for the data being transmitted. If the data is smaller than 46 bytes, it is padded with zeros to reach the minimum size. On the other hand, if the data is larger than 46 bytes, no additional padding is needed as the frame can accommodate it.