The correct option is A Iron
Nutrients in plants are classified into macronutrients and micronutrients based on the quantity in which they are required.
∙ Macronutrients are nutrients needed by plants in large quantities, for example, nitrogen, phosphorus, potassium and calcium.
∙ Micronutrients are nutrients utilized by plants in small quantities, for example, iron, magnesium, zinc and manganese.