Final answer:
The ozone layer is part of the A. stratosphere, which is the second layer of the Earth's atmosphere and contains the majority of atmospheric ozone that absorbs harmful ultraviolet radiation.
Step-by-step explanation:
The ozone layer is a vital part of the Earth's atmosphere which protects living organisms by absorbing the majority of the Sun's harmful ultraviolet (UV) radiation. The correct answer to the student's question is A. stratosphere.
The stratosphere is the second layer of the Earth's atmosphere, extending from about 6 miles (10 kilometers) to 31 miles (50 kilometers) above the Earth's surface. This layer is where the majority of the ozone layer is found. The ozone in this layer is crucial for life on Earth as it filters out potentially damaging ultraviolet light from reaching the Earth's surface, thus protecting the biosphere from UV-B radiation that can lead to skin cancer and genetic damage.
Measures taken to preserve the ozone include international agreements to phase out substances that deplete it, such as chlorofluorocarbons (CFCs), and these efforts have led to a gradual recovery of the ozone layer.