Normal cells stop growing (reproducing) when enough cells are present. For example, if cells are being produced to repair a cut in the skin, new cells are no longer produced when there are enough cells present to fill the hole (when the repair work is done).
In contrast, cancer cells don’t stop growing when there are enough cells present. This continued growth often results in a tumor (a cluster of cancer cells) being formed.
Almost positive that it's option C, because ultraviolet rays indeed do that, i'm not good with the study of x-rays but i'm sure it doesn't go with #3.
Mitochondria are the power plants of the cells.
O1:2:1 because they are carbon, hydrogen and oxygen
A complex chemistry is most related to maintaining a stable internal environment.
