(a) potassium, phosphorus, selenium, boron
(b) magnesium, sulphur, iron, zinc
(c) phosphorus, potassium, sulphur, calcium
(d) calcium, magnesium, manganese, copper.
Ans : (c) phosphorus, potassium, sulphur, calcium.
Macroelements (macronutrients) are those essential elements which are present in easily detectable quantities, i.e., 1-10 mg per gram of dry matter. Macroelements are usually involved in the synthesis of ! organic molecules and development of osmotic potential. They are nine in number ' C, H, O, N, P, K, S, Mg and Ca.