Correct Option: B

Magnesium is a macronutrient. Micronutrients are essential elements that are required by plants in small amounts. They include Fe, Cu, B, Mo, Mn, Cl, and Ni. Macronutrients, on the other hand, are those essential elements that are required by plants in larger amounts. The examples include C, H, O, N, S, P, K, Ca and Mg.