The most likely answer here would be that all of these processes are involved in the transmission of a nerve message.
The reason for this is because - the sodium-potassium pump and exocytosis are two essential processes that happen during every action potential, they are actually what makes the action potential be what it is. At the same time it's true that diffusion happens because it has to be present to a certain degree in order for the nerve message to be pased all the way from a fingertip to the brain.
