Fact 1: Antibodies are large, Y-shaped proteins that recognize and bind to antigens.

Fact 2: Antigens are expressed by cancer cells.

Given the two facts above, answer the question "what do antibodies recognize and bind to?" with the following options: 
- humans
 - vitamins
 - h2o
 - harmful substances
 - cancer cells
 - electrons
 - the skin
 - protect them


 

     cancer cells    