Which of the following refers to a decline in the fertility of land and quality of soil?

None of the above

The correct answer is Option 4: None of the above

Land degradation is the deterioration or loss of the productive capacity of the soils for present and future. 

Ozone depletion refers to the depletion of ozone in the layer which is found in "stratosphere".

Deforestation is the purposeful clearing of forested land.

Global warming refers to increase in the average temperature of the planet.