JEE Advanced levelSingle correct optionDifficulty 3 of 3ev045
Which statement correctly contrasts ozone in the two regions of the atmosphere?
AOzone is a primary pollutant emitted directly by vehicles in the troposphere
BOzone formed in photochemical smog is a harmful tropospheric pollutant, whereas stratospheric ozone is beneficial because it absorbs harmful ultraviolet radiation
COzone is harmful in the stratosphere and beneficial in the troposphere because it absorbs ultraviolet radiation near the ground
DOzone is harmful in both regions because it is a strong oxidising agent
Answer: B
In the troposphere, OX3 forms from NOX2 photolysis and O+OX2OX3; it irritates the respiratory tract and damages plants, so it is a secondary pollutant. In the stratosphere the ozone layer absorbs harmful UV and protects life. Ozone is not emitted directly by vehicles.