Which one is dominating salt in alkali soil

Answer: Option D

Na₂CO₃ is the dominating salt among the given options in alkali soil. Alkali soils owe their unfavorable physio-chemical properties mainly to the dominating presence of sodium carbonate, which causes the soil to swell and difficult to clarify and settle.
Alkali soils are clay soils with high pH, a poor soil structure and a low infiltration capacity. They have a hard calcareous layer at 0.5 to 1 meter depth.