In step 4 of the CSMA/CA protocol, a station that successfully transmits a frame begins the protocol to transmit a second frame at step 2, rather than step 1.What rationale could justify this procedure over simply transmitting the second frame immediately (if the channel is sensed idle)?

Using CSMA/CD to avoid collision.

Explanation:

If the channel is detected idle then the station does not transfer the second frame to avoid the collision by design of the CSMA/CD (Carrier sense multiple access / Collision detection). When received the protocol for first frame, a station to send second frame begins at step 2 rather than step1.

Explanation :

•Station A and Station B are transfers data frames, remain all not want to transmit data. In this situation, station A find the channel to be idle and send first frame then next second frame.  

•Similarly B received the transfer data at the same time. Then leads to collision.  

•Using CSMA/CD to avoid collision.