Which of the following are controlled-access protocols: A. Reservation B.…

Correct answer: Reservation, Polling, TDMA, and Token Passing.

• Reservation: stations reserve time or bandwidth so transmissions are scheduled and collisions are avoided; this is a controlled-access method.

• Polling: a central controller polls each station and grants permission to transmit, enforcing controlled access.

• TDMA: time-division multiple access allocates specific time slots to users so only the assigned user transmits in its slot, making it a controlled-access technique.

• Token Passing: only the station holding the token may transmit, which enforces controlled access and prevents collisions.

• CSMA/CA: carrier-sense multiple access with collision avoidance is contention-based (stations compete for the medium) and is not a controlled-access protocol.

Note: None of the provided answer choices lists exactly the correct set. The choice that lists Reservation, Polling, and Token Passing is closest but omits TDMA, which should also be included.