- A Nitrogen-Phosphorus-Potassium, the three macronutrients
- B Nitrogen-Protein-Krypton, an invalid combination
- C Nitrite-Phosphate-Kelp, not a real fertilizer label
- D Nitrogen-Phosphorus-Kalium (potassium)
Correct answer: D. Nitrogen-Phosphorus-Kalium (potassium)
Explanation: NPK fertilizers contain Nitrogen (N), Phosphorus (P), and Potassium (K, from Kalium). These are the three macronutrients most commonly deficient in agricultural soils and most important for plant growth.
Concept context
Essential mineral elements, their roles and deficiency symptoms. Nitrogen fixation and soil nutrition.