The sun's radiation and air pollution in the external environment will cause the body to generate more reactive oxygen free radicals. The reactive oxygen radicals in the body are the root of human aging, and antioxidants can effectively remove excess free radicals in the body. If the above description is true, which of the following must be true? ['Eliminate excess free radicals in the body, either avoid sunlight radiation and air pollution, or ingest antioxidants.', 'The speed of human aging may be determined by the environment and may also be affected by antioxidants.', 'Severe air pollution affects the speed of aging and the effectiveness of antioxidants.', 'Antioxidants can effectively extend human life.']