What is fertilizer?

• A. A pesticide used to kill insects
• B. A device for applying water
• C. A fungus
• D. A chemical or natural substance added to soil to increase its fertility

Answer: (D)

Fertilizer supplies essential nutrients to plants, improving soil fertility. It can be chemical (synthetic) or natural (organic such as manure or compost) and is used to correct nutrient deficiencies and boost growth and yields. Fertilizers are applied in various forms—granular or liquid—and labeled with the amounts of key nutrients (like nitrogen, phosphorus, and potassium) they provide, sometimes with added micronutrients. Proper use increases nutrient availability to plants and helps them grow robustly, while overuse or improper application can waste product and harm the environment. The other options describe a pesticide for pests, an irrigation device, and a fungus, none of which enhance soil fertility.