Final answer:
Layer 3 switches function to route traffic between devices across different VLANs by using IP addresses to make forwarding decisions, enabling communication between separate VLANs and IP subnets.
Step-by-step explanation:
The function of Layer 3 switches is primarily to route traffic between devices that are on different VLANs (Virtual Local Area Networks). Unlike traditional switches that operate at Layer 2 and use MAC addresses to forward Ethernet frames within the same VLAN, Layer 3 switches can perform routing functions based on IP addresses. Therefore, the correct answer to the question is 'A. They route traffic between devices in different VLANs.'
Layer 3 switches are capable of making forwarding decisions based on logical addressing (IP addresses), which enables communication between separate VLANs and different IP subnets. This is essential in large and segmented network environments. Layer 3 switches do not operate exclusively on broadcasting traffic as routers would limit the scope of broadcast domains. They also don't forward Ethernet frames using only MAC addresses, as that is a function more associated with Layer 2 operations.