Explanation

A is correct because Nitrogen (N), Phosphorus (P), and Potassium (K) are the three primary macronutrients essential for plant growth. B is incorrect because Carbon (C) is generally considered an organic element source rather than one of the three main required mineral elements in this context. C is incorrect because it lists N, K, but omits a third key nutrient like P or another major component. D is incorrect because while Nitrogen and Phosphorus are vital, Sulfur (S) is often grouped with other secondary nutrients, making NPK the standard answer for 'three core elements'.