The transport of certain molecule exhibits the following characteristics: the molecule moves down i

That's what I think

The transport of certain molecule exhibits the following characteristics: 
1)   The molecule moves down its concentration gradient= Passive Transport (no energy required)
2)   The molecule at concentrations above a given level= Active Transport (requires energy)
3)   The rate of transport does not increase= Passive Transport (equilibrium, diffusion stops when the concentration on either side of the membrane is equalized)
4)   Cellular energy is not required for transport to occur= Passive Transport (no energy required)

Which transport process is at work?  It's evident that process #2 (active transport mechanisms) is at work.