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Which of the following best completes the passage below? A recent investigation was carried out to assess whether overhead power cables had any adverse health impacts. The researchers examined individuals residing within 250 meters of high-voltage cables over a 10-year span and searched for statistically significant increases in rates of over 800 health issues. The findings indicated that the rate of childhood leukemia was five times greater among those living nearest to the power cables. However, this statistic alone should not raise concern, because__________________________.