How does a device know that the media is free before transmitting data in a network that uses

CSMA$/$CD$?$

a$.$ The device waits for its turn before transmitting.

b$.$ The device sends a special signal to request access to the media.

c$.$ The device sends a message to all other devices on the network, asking for the transmit token.

d$.$ The device listens for signals on the media to check if it's busy.