Full-duplex Ethernet — which link types can operate in full duplex? From the list of common Ethernet connections, select all that can legitimately operate in full-duplex mode (no collisions) when supported by the devices and cabling.

Introduction / Context:
Full-duplex Ethernet removes collisions by allowing simultaneous send and receive on twisted pairs or fiber. Knowing which device pairs can run full-duplex is essential for configuring links correctly and avoiding mismatch errors that degrade performance.

Given Data / Assumptions:

• Choices: (1) Hub to hub, (2) Switch to switch, (3) Host to host, (4) Switch to hub, (5) Switch to host.
• Devices support full-duplex and autosensing where applicable.
• Hubs are half-duplex by design (shared collision domain).

Concept / Approach:
Full-duplex requires a point-to-point link with no shared collision domain. Switch ports are full-duplex capable; hubs are not. Two modern NICs directly connected (with appropriate cabling or auto-MDI/MDI-X) can negotiate full-duplex as well. Therefore, valid full-duplex pairs are switch-to-switch, switch-to-host, and host-to-host. Hub-involved links remain half-duplex.

Step-by-Step Solution:
Eliminate any option containing a hub as an endpoint for full-duplex (1 and 4 are invalid).Confirm switch-to-switch is full-duplex capable (2).Confirm switch-to-host is full-duplex capable (5).Confirm host-to-host can run full-duplex with proper cabling (3).Combine valid pairs: 2, 3, and 5.

Verification / Alternative check:
On Cisco gear, show interfaces displays duplex settings. Two hosts linked directly (for example, lab PCs) will negotiate full-duplex if NICs and drivers support it.

Why Other Options Are Wrong:

• A/B: Include hub links which cannot be full-duplex.
• E: Omits switch-to-switch, which is full-duplex capable.

Common Pitfalls:
Duplex mismatches (one end half, the other full) create late collisions and FCS errors. Always verify both ends negotiate or statically match.

Final Answer:
2, 3 and 5