The correct answer is It manages MAC addresses and handles local frame transmission.

The link layer is responsible for framing, MAC addressing, and the delivery of frames on a single network segment. Understanding the link layer helps you reason about how switches forward traffic, how ARP resolves layer 3 addresses to MAC addresses, and how VLANs and bridging affect local traffic patterns.

Knowing the link layer matters for security because many controls and attacks operate at this level. Defenses such as port security, MAC filtering, dynamic ARP inspection, and MACsec act on link layer concepts. Learning the link layer lets you design network segmentation and local traffic handling to limit broadcast domains and reduce attack surface.

It supplies encryption across an entire communication path is incorrect because link layer protections are generally hop by hop. There are link layer encryption technologies, but they protect the link between two devices and do not by themselves provide end to end encryption for an entire path.

It decides end to end internet routing paths is incorrect because routing decisions that determine end to end paths are made at the network layer. Routers and routing protocols work with IP addresses and do the path selection that spans multiple links.

It obviates the need for the physical signaling layer is incorrect because the physical layer remains necessary. The physical layer carries the electrical or optical signals and defines the media and signaling that the link layer depends on to transmit frames.

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