Which of the following describes an incomplete fertilizer?

An incomplete fertilizer is defined by its composition; specifically, it contains two or fewer of the primary macronutrients: nitrogen (N), phosphorus (P), and potassium (K). This means it can have one or two of these elements but not all three.

The correct choice reflects this definition by indicating that it contains N, P, or K, but specifically states that it does not include all three. This is in contrast to a complete fertilizer, which would require all three macronutrients to be present in its formulation.

In the context of the other options, the first suggests that an incomplete fertilizer contains all three macronutrients, which directly contradicts the definition. The second implies that the fertilizer contains solely nitrogen and phosphorus, thus leaving out potassium, which could indeed define a type of incomplete fertilizer, but does not encompass the full range of incomplete fertilizers that may also include only potassium or any other combination without all three present. Lastly, the fourth option describing a fertilizer that contains only micronutrients does not align with the concept of macronutrients at all, further clarifying that incomplete fertilizers refer specifically to a lack of one or more of the primary macronutrients rather than focusing on micronutrients.

Therefore, the correct understanding of an incomplete fertilizer