Difference between topsoil and subsoil

subsoil is the layer underneath the surface topsoil, which consists of greater minerals and materials of iron and aluminium compounds than topsoil. The subsoil tends to be more compact than topsoil, since it does not hold any air in the soil.

Explanation:

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the answer is "a.) well–developed vascular system."

explanation:

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.