Concept:Root hairs take in mineral ions through transport mechanisms that move salts, not water.
Explanation:Osmosis moves only water molecules across a semi-permeable membrane, so it cannot absorb dissolved mineral salts directly.
This eliminates options A and B.
Imbibition is the absorption of water by solid colloidal particles, which does not bring mineral salts into the root; this eliminates option D.
When the concentration of mineral salts in the soil solution is higher than in the root hair cell, the salts enter the root by diffusion down the concentration gradient.
However, mineral salts are usually present in very low concentrations in the soil.
In that case, carrier proteins on the root hair cell membrane bind the mineral ions and move them into the cell against the concentration gradient.
This movement requires energy in the form of
ATP and is called active transport.
Therefore, mineral salts are absorbed into roots by both diffusion and active transport.
Answer:C. Diffusion and active transport.