On an Ethernet network, which medium access control method is used to control how devices share the transmission medium?

Introduction / Context:
Ethernet is the dominant LAN technology and historically used a specific medium access control (MAC) method to manage how multiple devices share a common medium. On classic shared Ethernet segments, collisions could happen when two devices transmitted simultaneously. Carrier Sense Multiple Access with Collision Detection (CSMA/CD) was designed to reduce and manage these collisions.

Given Data / Assumptions:

We are referring to traditional Ethernet as defined by IEEE 802.3.
Devices share a common collision domain, such as on a coaxial bus or a hub based star topology.
The question asks specifically which connection or access mechanism Ethernet uses.

Concept / Approach:
CSMA/CD stands for Carrier Sense Multiple Access with Collision Detection. "Carrier sense" means a device listens before transmitting to check whether the medium is idle. "Multiple access" means many devices share the same medium. "Collision detection" means that if a device detects a collision while transmitting, it stops, sends a jam signal and backs off for a random time before trying again. This mechanism is central to classic half duplex Ethernet operation. Although modern switched full duplex Ethernet largely eliminates collisions, CSMA/CD remains part of the original Ethernet specification.

Step-by-Step Solution:
Recall that token passing is associated with technologies like Token Ring and FDDI, not Ethernet. CSMA/CA is used by wireless LAN technologies such as IEEE 802.11, which cannot reliably detect collisions on the air and therefore try to avoid them. Host polling and TDMA are used in other networking systems but are not part of the standard Ethernet MAC method. CSMA/CD is explicitly named in Ethernet and IEEE 802.3 standards as the access method, making option b the correct answer. Therefore, Ethernet uses CSMA/CD as its connection and access mechanism on shared media networks.

Verification / Alternative check:
Textbooks and Cisco training material describe the historical "Ethernet bus" or "hub based Ethernet" networks as CSMA/CD systems. You can also see CSMA/CD referenced in configuration outputs and documentation describing half duplex Ethernet behavior. This cross checks the exam style statement that Ethernet uses CSMA/CD.

Why Other Options Are Wrong:
Option a (token passing) relates to Token Ring LANs where a token circulates and only the holder may transmit, which is a different MAC approach.
Option c (CSMA/CA) is specific to wireless LAN technologies and is not used by wired Ethernet.
Option d (host polling) is a centralized method where a controller polls each device, which is not how Ethernet works.
Option e (TDMA) divides the channel into fixed time slots, used in some WAN and cellular systems, not in classic Ethernet.

Common Pitfalls:
Learners sometimes confuse CSMA/CD and CSMA/CA, especially when studying both wired and wireless networking. Remember the simple association: "D" for "detection" in wired Ethernet, "A" for "avoidance" in Wi-Fi. Also note that CSMA/CD is practically obsolete on modern full duplex switched Ethernet, but it remains an important concept for understanding legacy networks and exam questions.

Final Answer:
Ethernet uses CSMA/CD (Carrier Sense Multiple Access with Collision Detection) as its medium access control method.