The correct answer is option 3.The frames must be held before they are used if the date of the frames arrives at the receiver side faster than they can be processed. The receiver, in most cases, does not have enough storage space, particularly if it is receiving data from multiple sources. Frames may be discarded or service may be denied as a result of this. To keep the receiver from being overloaded by the frames, we need to tell the sender to slow down. This can only be achieved by input from the receiver to the sender.The protocol we'll talk about now is called Stop and Wait because the sender sends one frame, then waits for confirmation from the receiver before sensing the next frame. Although data frames still require unidirectional communication, axillary acknowledgement frames travel in the opposite direction.? Hence the correct answer is Simplex stop and wait protocols.