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


 

  cancer       