Explanation:

The three main ingredients in most complete fertilizers, often referred to as primary macronutrients, are Nitrogen (N), Phosphorus (P), and Potassium (K). These elements are required by plants in larger quantities for healthy growth and development. Nitrogen is crucial for leaf growth and protein synthesis. Phosphorus is essential for root development, flowering, and fruiting. Potassium contributes to overall plant vigor, disease resistance, and water regulation. While calcium and sulfur (mentioned in other options) are also essential plant nutrients (secondary macronutrients), N-P-K are universally recognized as the primary components of fertilizers.