A study revealed lesser incidence of carcinoma colon in pure vegetarians than non vegetarians by which it was concluded that B(bata)- carotene is protective against cancer.This may not be true because the vegetarian subjects may be consuming high fiber diet which is protective against cancer.This is an example of:

• A. Causal association
• B. Multifactorial causation
• C. Common association
• D. Confounding factor