Some researchers have pointed out that since the Industrial Revolution, the capacity and scope of human activities have increased significantly. At the same time, the pH of the ocean has gradually decreased. Therefore, there is a causal relationship between human activities and changes in the ocean, which will Causes irreversible damage to marine ecosystems. However, opponents believe that the carbon dioxide contained in the atmosphere is the culprit for ocean acidification. Without the oceans absorbing carbon dioxide, the carbon dioxide in the atmosphere is much higher than current levels and global warming The impact will be even more serious. Which of the following, if true, would most weaken the opponent's point of view? ['Human activities before the Industrial Revolution did not cause ocean acidification.', 'Seawater acidity will drop to 7.8 by 2100, that is, seawater acidity will be 150% higher than in 1800.', 'Carbon dioxide will not be completely absorbed by the ocean, and a considerable part will remain in the atmosphere.', 'According to statistics, the carbon dioxide content in the atmosphere has increased significantly since the Industrial Revolution.']