Which of the following is a characteristic of NPK fertilisers?

The correct option is They improve agricultural productivity. This answer is correct because it matches the approved learning objective to define NPK fertilisers as fertilisers containing compounds of nitrogen, phosphorus and potassium. (Chemistry only) in the subtopic Production and uses of NPK fertilisers.

The correct option is They improve agricultural productivity. They improve agricultural productivity is correct because it directly supports the approved learning objective to define NPK fertilisers as fertilisers containing compounds of nitrogen, phosphorus and potassium. (Chemistry only). This belongs to the subtopic Production and uses of NPK fertilisers within The Haber process and the use of NPK fertilisers, so the explanation must stay tied to that curriculum context. The other options are incorrect because they either do not answer this learning objective, use a vague statement, or move away from Production and uses of NPK fertilisers.