As people's life and work gradually enter high-rise buildings, people have less exposure to sunlight. Studies have found that sunlight is a necessary condition for the synthesis of vitamin D, and vitamin D is a key factor to promote calcium absorption. Therefore, some people have concluded that More susceptible to diseases caused by calcium deficiency, such as osteoporosis. Which of the following is true and the above conclusions can be questioned most? ['Patients with osteoporosis can be relieved or cured by exposure to the sun.', 'Calcium-containing foods in the conceptual structure of modern people are much richer than before.', 'Patients with osteoporosis are exposed to sunlight for the same length of time as others.', 'Oral vitamin D tablets are a synthetic formula added with absorption enhancers.']