There are two properties that affect the conduction speed of an action potential along an axon: die axon's diameter and whether or not the axon is myelinated. rank the axons from slowest to fastest conduction speed. if two axons have the same conduction speed, place one on top of the other.

 Axons with high  diameter, and myelinated will conduct action potential faster.

Axons with low diameter but myelinated will be  relatively  slow in the speed of action potential transmission

Axons with high diameter and unmyelinated will be relatively slow in action potential transmission.  

Axons with low diameter, and unmyelinated will conduct action potential slowly .

Explanation:

Diameter of Axon affects conduction speed of Action Potential; the thick axons with  high diameter conducts action potential at a faster speed than thin neurons. This is because of the less resistance to the transmission of action potential along the thick axon. However, thin neurons with   lower diameter has more resistance to the action potential conduct along the axon, thus the speed of transmission is slow.  

Myelinated neuron transmits action potential faster because of   jumping of action potential at the nodes of Ranvier where there is highest concentration of all channel proteins and pump proteins, Therefore action potential is conducted at a faster rate as it jumps from one node to another. This is salutatory conduction. It increases the conduct about 50 times compare to unmyelinated neuron. In neuron of human it increases the speed to 100ms-1

.Conversely, unmyelinated neurone  conducts action potential slowly. About 0.5ms-1 . This is because no salutatory conduction takes place because there is no myelin interruption as Nodes of Ranvier