The researchers studied 13 cloned sheep, 4 of which were just replicas of the world's first somatic cloned sheep, "Dolly. " The researchers examined the musculoskeletal, metabolic, and blood pressure of these cloned sheep. The results were found to be in contrast to controls Compared with group sheep, these cloned sheep only had mild osteoarthritis, and only one was moderate. They had no symptoms of metabolic disease, normal blood pressure, and relatively healthy. Therefore, the researchers pointed out that the aging process of cloned animals was normal. Which of the following, if true, would most weaken the argument? ['The sheep in the control group in the study are younger than the sheep in the experimental group.', 'The world\'s first cloned sheep "Dolly" only survived 6 years.', 'Current somatic cell cloning technology is far from perfect.', 'Researchers fail to detect major molecular markers related to aging.']