In data communications, the term ‘‘full duplex’’ refers to simultaneous two-way transmission. In a full-duplex link, what can the sender and receiver do at the same time?

Introduction / Context:
Link directionality is a foundational networking concept that determines how two endpoints exchange information. Terms like simplex, half duplex, and full duplex describe whether data flows in one direction, alternates directions, or flows both ways at once. Understanding full duplex helps explain performance differences in Ethernet switching, serial links, and wireless systems that may be half duplex.

Given Data / Assumptions:

• We are discussing link behavior between exactly two endpoints (sender and receiver).
• ‘‘Full duplex’’ is being contrasted with half duplex and simplex.
• No special protocols or media are assumed; the concept is medium-agnostic.

Concept / Approach:
In full duplex, both endpoints transmit and receive at the same time over logically separate directions (two wires, two frequencies, two time slots, or echo cancellation on a single pair). This is different from half duplex, where only one station transmits at a time and the other must wait, and from simplex, where data flows only in one direction.

Step-by-Step Solution:

Verification / Alternative check:
Modern switched Ethernet at 1 Gbps and above operates full duplex, allowing frames to be sent and received concurrently without collisions. In contrast, traditional hub-based Ethernet was half duplex and relied on collision detection or avoidance.

Why Other Options Are Wrong:

• ‘‘can send or receive data one at a time’’ describes half duplex, not full duplex.
• ‘‘cannot talk at once’’ also implies half duplex.
• ‘‘one-way data transmission only’’ defines simplex.
• ‘‘None of the above’’ is incorrect since one option is exactly right.

Common Pitfalls:
Assuming wireless links are always full duplex; many Wi-Fi links are effectively half duplex due to shared medium constraints. Also, users sometimes conflate full duplex with ‘‘twice the speed’’; actual throughput depends on workload symmetry and protocol overhead.

Final Answer:
can receive and send data simultaneously