The third number on a fertilizer analysis indicates the amount of which element as being present in the product

Most fertilizer bags are marked with three numbers, which represent the amounts of the following chemicals: nitrogen, phosphorus, and potassium. The third number represents the amount of potassium in the fertilizer. All three of these chemicals are important for plants, but different plants require different amounts of these chemicals, so the label helps consumers determine which product to buy.

The answer is c) pyrite