To solve this problem, we need to identify which zone of the atmosphere contains the ozone layer. Let's analyze each option:$\newline \bullet$Option 1: Ionosphere$\newline$ - The ionosphere is a part of the atmosphere that is ionized by solar and cosmic radiation. It is not known for containing the ozone layer.$\newline \bullet$Option 2: Mesosphere$\newline$ - The mesosphere is the third layer of the atmosphere above the stratosphere. It does not contain the ozone layer.$\newline \bullet$Option 3: Stratosphere$\newline$ - The stratosphere is the second layer of the atmosphere above the troposphere. It contains the ozone layer, which absorbs and scatters ultraviolet solar radiation.$\newline \bullet$Option 4: Troposphere$\newline$ - The troposphere is the lowest layer of the atmosphere where weather occurs. It does not contain the ozone layer.$\newline$Based on this analysis, the correct answer is Option 3: Stratosphere, as it is the zone of the atmosphere that has the ozone layer.