Concept:Ozone in the stratosphere absorbs harmful ultraviolet radiation from the Sun.Explanation:The Sun emits high-energy ultraviolet (UV) rays that can damage living cells and cause skin burns.The stratosphere contains a layer rich in ozone, O3.This ozone layer acts as a shield by absorbing most of the Sun's UV radiation before it reaches the Earth's surface.Therefore, ozone is the atmospheric gas most useful in protecting humans from the Sun's harmful radiation.Answer:B. ozone