The A horizon is a surface horizon that largely consists of minerals (sand<span>, </span>silt<span>, and </span>clay) and with appreciable amounts of organic matter. This horizon is predominantly the surface layer of many soils in grasslands and agricultural lands.<span>These </span>materials typically<span> accumulate through a process termed illuviation, wherein the </span>materials<span> gradually wash in from the overlying.</span>
Answer is: c. It is incorrect because sodium phosphate is a compound that has a single composition.
Sodium phosphate is chemical compound composed of atoms connected with chemical bonds.
Pure substance is made of only one type of atom (element) or only one type of molecule (compound), it has definite and constant composition with distinct chemical properties.
Pure substances can be separated chemically, not physically, that is difference between pure substances and mixtures.
