Concept:The area marked Y is in the South-Eastern states of Nigeria, and the loose surface materials there make gully erosion its major environmental problem.
Explanation:Environmental problems are the harmful effects of human and natural activities on the biophysical environment.
The area marked Y lies within the South-Eastern states of Nigeria.
This region is underlain by weak, unconsolidated sandy and clayey soil materials.
These loose surface materials are easily removed by running water.
Heavy seasonal rainfall and sparse vegetation cover increase the rate of soil removal.
The continuous washing of the soil creates deep channels on the land surface.
These deep channels are known as gullies.
Gully erosion therefore occurs rapidly and becomes the dominant environmental problem in the area.
Drought is more common in the northern part of Nigeria, while oil pollution is associated with the Niger Delta region.
Insect pests do not pose a major environmental threat when compared to the destructive effect of gully erosion in the area.
Answer:B. Gully Erosion