Answer:
The 3 most common is:
Exposure to the sun: Having large amounts of exposure to the sun could cause blisters and sunburns, which can cause cancer cells to be created.
Cells become abnormal: Cancer cells in itself are "abnormal" in itself, and so this is your answer, as it's the definition on how cancer is created.
Exposure to chemicals: Most chemicals can cause cancer as the carcingon is implanted in your body through... exposure to the substance.
