Option C.
CSMA/CD stands for Carrier Sense, Multiple Access with Collision Detection.
- Carrier Sense: All nodes can distinguish between idle and busy links.
- Collision Detection: Node listens as it transmits can tell if it collides with another frame.
- Listen before transmit:
- If the channel sensed idle then transmit the entire frame.
- if the channel sensed busy then defer transmission.
Any station that wants to transmit a frame, or is currently transmitting a frame must continuously keep sensing the channel, to detect if the channel is idle and to detect collisions respectively.
In CSMA/CD, when a collision is detected the involved stations must immediately stop transmitting. When their "sensed" data does resemble the data they're sending; they know collision has occurred. But sometimes, for example, when a collision of $0$ Volts occurs, it is impossible to detect collision. Hence, we use a maximum $48$-bit jamming signal which announces the occurrence of collision .the purpose of the jamming signal is to tell all other stations that a collision has occurred.
References:
