Concept:Contention is a media-access condition where multiple stations attempt to transmit at the same time on a shared medium.Explanation:Contention occurs when two or more data stations on a shared channel try to send data simultaneously.In contention-based access, each station competes for the medium instead of being scheduled.This condition is used in protocols like CSMA/CD, where devices transmit as soon as the medium becomes free.If two stations transmit at the same time, it causes a collision, but the underlying condition is called contention.Answer:D. Contention