Answer:
D. Lung cells
Step-by-step explanation:
There are many organizations of living things and parts of living things. From simplest to complex the levels are: cells, tissue, organ, system, organism. So, if you have lung tissue then the only simpler organization is cells. These are simpler because cells are what make up tissue, just as tissue makes up organs. Through the levels, the more simple something is then the smaller it is, relatively.