Final answer:
ATM is not primarily used in Ethernet networks.
Step-by-step explanation:
One of the statements regarding asynchronous transfer mode (ATM) that is false is that it is primarily used in Ethernet networks (option C). ATM is a switching technique that was commonly used in the past for data transfer, but it is not commonly used in Ethernet networks today. Instead, Ethernet networks typically use other technologies such as Ethernet switches.