What is a downside to using parallel transmission?

Using parallel transmission involves multiple wires or channels to transmit data simultaneously. This can lead to various issues, particularly interference between the wires. As the number of wires increases, the potential for crosstalk or electromagnetic interference also rises, especially over longer distances. Each wire can pick up signals from adjacent wires, causing the data to become corrupted or less reliable.

This is particularly problematic because parallel transmission works best over short distances where the interference can be minimized. In scenarios where signals must travel further, the disadvantages of increased interference and the complexity of managing multiple connections become more pronounced. Therefore, the correct answer is that parallel transmission uses more wires, which can indeed lead to interference.