Alzheimer's disease is a relatively serious disease, and the mutation of gene 4 was once thought to be a causative factor of Alzheimer's disease. However, some scientists have recently suggested that the cause of this complex disease may be simple, that is, Some microorganisms that can cause brain infections, such as the HSV-1 virus. Which of the following, if true, would best support the above-mentioned scientist's point of view? ["People who carry the mutation 4 gene and are infected with HSV-1 virus are twice as likely to develop Alzheimer's disease than those who have such mutations alone.", 'When the mouse brain was infected with HSV-1, mice carrying the mutant gene 4 produced 14 times more viral DNA than normal mice.', 'Some patients with mutation # 4 have improved their condition after treatment with antiviral drugs.', 'The HSV-1 virus is also present in the brains of some healthy older adults.']