Which one of the following is a mixed fertilizer?

1. A mixed fertilizer is a fertilizer that contains two or more of the primary plant nutrients: Nitrogen (N), Phosphorus (P), and Potassium (K). 2. Urea primarily supplies Nitrogen (N). Its chemical formula is CO(NH₂)₂. 3. Ammonium Sulphate ((NH₄)₂SO₄) primarily supplies Nitrogen (N) and also some Sulphur (S). 4. Calcium Ammonium Nitrate (CAM), likely referring to CAN (Calcium Ammonium Nitrate), primarily supplies Nitrogen (N) and Calcium (Ca). 5. NPK fertilizers are specifically formulated to contain a mixture of Nitrogen (N), Phosphorus (P), and Potassium (K) compounds in varying proportions. They are the quintessential example of mixed fertilizers. 6. Therefore, NPK is the mixed fertilizer among the given options.