Which of the Following Is NOT Evidence Collected Indicating That

Which of the following is NOT evidence collected indicating that Helicobacter pylori plays a primary role in the genesis of ulcers?

A) Antibodies to the bacterium have been found in the serum of healthy controls.
B) This bacterium is present in the stomachs of a large proportion of individuals with ulcer disease.
C) Twenty percent of people who test positive for the bacterium show evidence of ulcer.
D) Animals injected with H. pylori suffered from ulcer disease.
E) The condition of patients treated with drugs to kill H. Pylori improves.