What happens to a message placed by a network node onto a channel using Time Multiple Access $($TDMA$)$ multiplexing?

a$.$ The message's bits are modulated on to a dedicated frequency carrier so it can share radio spectrum with other messages at the same time

b$.$ The message's bits are sent down the channel in different time slots shared with other messages in a round robin fashion

c$.$ The message is separated into bits and each bit is sent individually on its own wire to the destination node where all bits are reassembles at the same time into the original message

d$.$ The source node's message is appended to a "token" when the token reaches the source mose, and the com