There is a scientific experiment performed on 500 women aged 25 to 35 years. Two experimental groups were set up. The first group of subjects took aspirin for a long time, and the second group of subjects did not take aspirin. The results showed that the eyes of those who took aspirin for a long time were better than those who did not Aspirin wrinkles appear late in the corners of the eyes, and the skin is smooth and tender. This experiment shows that aspirin may become a cheap and effective anti-wrinkle and youth-preserving drug. Which of the following, if true, would best support the above conclusion? ['The eyes of the two groups of subjects were equivalent before the experiment.', 'Equal numbers of subjects in both groups.', 'The first group of subjects took a larger amount of aspirin.', 'Aspirin is synthetic.']