In one experiment, half of the subjects were the experimental group and consumed a large amount of some peppers. The other half of the control group did not eat the peppers. As a result, the experimental group's cognitive ability was much worse than the control group. This result is due to vitamin E, a major component of this pepper. Which of the following, if true, would be most helpful in proving that the ingredients in this pepper contributed to this experimental conclusion? ['The vitamin E mentioned in the above conclusion is found in all vegetables. In order to ensure nutrition, a certain amount of this vitamin E must be ingested.', 'The amount of peppers consumed by people in the experimental group is within the safe amount prescribed by the government food regulations.', 'In the second experiment, only one group that consumed a lot of peppers was used as the experimental group, and no control group that did not consume peppers was given.', 'Before the experiment, the two groups of subjects were equally divided according to their cognitive ability.']