The correct answer is (a) and (d) only. Explanation & Key Takeaways: Salinity: • The salt content of the soil determines its salinity, and the process of raising the salt content is known as salinization. • Natural processes like mineral weathering or the slow retreat of an ocean can also result in salination. • It may also result from man-made activities like irrigation and salting of the roads. • Irrigation in the fields of saline tracts affects the productivity of crops. • Although soil salinization is a major issue in and of itself, it seldom occurs by itself. Hence, statement (d) is correct. • Due to the insufficient circumstances for plant growth, salinity results in a constant wetting of the ground surface and a lack of cover. • These increase the likelihood of erosion in areas. This leads to the Degradation of soil structure. Hence, statement (a) is correct.