Step 1: Recall the layers of the atmosphere from the ground upwards: troposphere → stratosphere → mesosphere → thermosphere → exosphere. Step 2: The ozone (O₃) layer lies in the lower stratosphere, roughly 15–35 km above the Earth. Step 3: It absorbs most of the Sun's harmful UV radiation, protecting us from skin cancer and cataract. Step 4: The troposphere is where weather and clouds occur, so it is not the answer. Answer: Stratosphere.