Answer:
D. Lung cells
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.
In the late 1950's - 1960's survival from cancer was poor. Damaging surgery and relatively unsophisticated radiotheraphy were the main treatments. Understanding of cancer treatment has transformed over 60 years. The arrival of chemotheraphy, and solid evidence for the link between cancer and factors such as smoking or viruses.
The first cells were probably photosynthetic
