Please answer the following question: Fact 1: Cells that divide uncontrollably may form a tumor, or abnormal mass of cells. Fact 2: Cancer begins when a cell begins dividing uncontrollably. Given the two facts above, answer the question "what can cause a tumor to form?" with the following options: - parasites - cancer - respiration - digestion - pesticide - radiation - ovaries - weathering
A:
cancer