The primary nutrients for plants are essential elements that are required in large quantities for healthy growth. Option 1, which includes Nitrogen, Phosphorus, and Potassium, is the correct answer.

Nitrogen is necessary for the production of proteins, enzymes, and chlorophyll, which are essential for plant growth. Phosphorus plays a crucial role in energy transfer, root development, and flowering. Potassium helps regulate water movement, enhances disease resistance, and aids in the overall growth and development of plants.

Option 2, which includes Nitrogen, Oxygen, and Silicon, is incorrect as Oxygen is not a primary nutrient for plants, although it is required for respiration. Silicon is considered a beneficial element but is not one of the primary nutrients.

Option 3, which includes Potassium, Boron, and Nitrogen, is incorrect as Boron is not one of the primary nutrients.

Option 4, which includes Nitrogen, Phosphorus, and Iron, is incorrect as Iron is not one of the primary nutrients.