AIIMS 2019 Botany Macronutrients MCQ Question

Option D is correct because it includes carbon (C), hydrogen (H), magnesium (Mg), and nitrogen (N), which are essential macronutrients for plants. Carbon and hydrogen are fundamental components of organic molecules, while nitrogen is crucial for amino acids and proteins, and magnesium plays a vital role in chlorophyll synthesis.

In contrast, options A, B, and C contain elements that are either micronutrients (like B and Zn) or not classified as macronutrients (like K and Mn), which do not fulfill the criteria for essential macronutrients needed in larger quantities for growth and development.