26. Which of the following statements about proto-oncogenes is NOT correct? (A) Proto-oncogenes are normal genes with the potential to become oncogenes. (B) Many proto-oncogenes code for growth factors. (C) A mutation occurring in a proto-oncogene can convert it to become an oncogene. (D) Proto-oncogenes are a type of carcinogens. (E) None of the above.