ANS:A - 5, 10, 5% respectively of N₂, P₂O₅ and K₂O.

When fertilizers are labeled with numbers such as 5-10-5, these numbers represent the percentage of nitrogen (N), phosphorus pentoxide (P2O5), and potassium oxide (K2O) in the fertilizer, respectively.

1. 5% Nitrogen (N): Nitrogen is an essential nutrient for plant growth and is a major component of chlorophyll, which is crucial for photosynthesis. It is responsible for promoting vegetative growth, leaf development, and overall plant vigor. In a 5-10-5 fertilizer, 5% of the content is composed of nitrogen.
2. 10% Phosphorus Pentoxide (P2O5): Phosphorus is another vital nutrient for plants, playing a key role in various metabolic processes, including energy transfer and the development of roots, flowers, and fruits. In fertilizer labels, phosphorus content is often expressed as phosphorus pentoxide (P2O5), which represents the oxide form of phosphorus. Phosphorus is crucial for seed germination, root development, and early growth stages of plants. In a 5-10-5 fertilizer, 10% of the content is composed of phosphorus pentoxide.
3. 5% Potassium Oxide (K2O): Potassium is a macronutrient that helps regulate water uptake and retention, enhances disease resistance, and promotes overall plant health and vigor. Similar to phosphorus, potassium content in fertilizers is often expressed as potassium oxide (K2O), which represents the oxide form of potassium. In a 5-10-5 fertilizer, 5% of the content is composed of potassium oxide.