In one study, researchers tracked medical data from 190,000 people born in the country between 1974 and 1994, who had undergone an intelligence test between 2006 and 2012. When doing an intelligence test, approximately Respondents were hospitalized due to infection. Researchers found that those who were hospitalized due to infection had an average IQ score of 1.76 points lower than those of the general population, and those who had been hospitalized 5 or more times due to infection had an average IQ score of 9.44 points lower than the average Researchers have pointed out that human infections can cause individual IQs to decline. Which of the following, if true, would most weaken the conclusion? ['Infection of tissues around the brain can affect brain intelligence.', 'Evidence suggests that infection affects cognitive ability in patients with dementia.', 'IQ is a method of evaluating mental capacity, and there are measurement errors.', 'Illness makes the patient nervous and not paying attention during the test.']