Media access control basics: which item below names a multiple-access channel access technique (MAC) rather than a signal property or impairment?

Introduction / Context:
On shared media, multiple stations contend to transmit. Media Access Control (MAC) techniques define rules for who can send and when. Distinguishing a MAC method from unrelated physical-layer terms or impairments is a foundational networking skill. This question asks you to pick the item that is actually a MAC technique for multiple-access media.

Given Data / Assumptions:

• We compare one MAC method with physical-layer concepts.
• Only one option corresponds to a contention-access protocol.
• We are not evaluating modulation quality or link loss.

Concept / Approach:
Aloha is a random-access MAC protocol originating from early packet radio networks. Stations transmit when ready; collisions may occur and are recovered by retransmission. Slotted Aloha improves efficiency by forcing transmissions to time slots. By contrast, amplitude is a waveform magnitude; angle modulation is a family of analog modulation methods (frequency/phase); attenuation describes signal loss over distance or media—not MAC behavior.

Step-by-Step Solution:

Verification / Alternative check:
Many textbooks trace Ethernet’s early design lineage through Aloha concepts, demonstrating Aloha’s role as a seminal MAC approach.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing modulation or channel impairments with MAC algorithms; MAC operates at the link layer, while modulation/attenuation are physical-layer concerns.

Final Answer:
Aloha.