Does Taking Vitamins Prevent Colon Cancer? a Study Assigned 864

Multiple Choice

Does taking vitamins prevent colon cancer? A study assigned 864 subjects at random to four groups. One group took beta-carotene, another took vitamins C and E, a third took all three, and the fourth group took only a dummy pill. After four years, there was no difference among the groups in the formation of polyps in the colon that precede cancer.
Earlier studies had shown that people who choose to eat a lots of vegetables containing these vitamins tend to have less colon cancer.

A) The earlier studies are more convincing than the new study because they involved thousands of people.
B) The results of the earlier studies could be due to some other fact about people who choose to eat a lot of vegetables.
C) The new study is more convincing because people were assigned to treatments at random, rather than choosing whether or not to take vitamins.
D) Both B and C are correct.
E) Answers A, B, and C are correct.