Q) Choose the incorrect pair---

1) Classical smog-------SO₂

2) Photochemical smog----------PANtO₃

3) Green house effect------------CFC

4) Eutrophication----------DDT

 i also think so,,,PAN is d correct option for (3), but it also contains -tO3 after i. so confused....

eutrophication --DDT

(1) Classical smog is a mixture of smog, fog and SO2

(2) Photochemical smog is made up of O3, Nitiric oxide, acrolein, formaldehyde and peroxyacetyl(PAN)

(3) CFC's cause greenhouse effect

(4) DDT is basically used to control the damages caused by insects, rodents, weeds and various crop diseases.

and Eutrophication is due to the presence of excessive nutrients in any water body due to inflow of nutrients from fertilzers that results in the increase of phosphate ions in water..

so no connection between DDT and Eutrophication

Hence the answer is (4)