Answer:
The correct answer will be option-D.
Step-by-step explanation:
Magnesium is a macro-nutrient element needed by the plant in high concentration as it is involved in the formation of chlorophyll structure, the cell membrane stabilization and the metabolism of carbohydrates.
The magnesium is absorbed from the soil as Mg ⁺² ions due to the differences in the concentration of the ions between the soil and plants. The main mechanism for absorption of these ions is passive diffusion which leads the movement of ions from low concentration to high concentration.
In the given question which states that if magnesium concentration is higher in the root hair cells than in the soil then these ions will move in the roots via special mechanism through transport proteins which require energy in the form of ATP to lead the movement of ions against a concentration gradient. This movement of ions is known as active transport.
Thus, option- D is the correct answer.