Wilson wants to reduce his risk of cancer. He doesn't smoke; his weight is healthy for his height; and he eats a wide variety of fruits and vegetables. Which of the following dietary changes should he make to reduce his risk of cancer?
a) When taken in the form of dietary supplements, vitamins may be less effective at reducing cancer risk than when the vitamins are consumed as they naturally occur in foods.
b) Most dietary supplements do not provide high enough amounts of vitamins to be effective.
c) Most dietary supplements aren't effective in reducing the risk of cancer because they don't contain organic formulations of vitamins.
d) According to studies involving human subjects each dietary supplement that contains vitamins must be taken in balanced amounts to reduce the risk of cancer.