In fertiliser terminology, “NPK” denotes a product containing nitrogen, phosphorus, and potassium together. In general usage, NPK refers to which broad type of fertiliser?

Introduction / Context:
NPK-labelled products deliver the three primary macronutrients in one application. Depending on manufacturing, these may be physical blends (mixed fertilisers) or chemically combined granules (complex fertilisers). Many curricula and general usage equate the term “NPK” on a bag with a mixed fertiliser when contrasted against single-nutrient straights.

Given Data / Assumptions:

• NPK indicates simultaneous presence of N, P, and K.
• Options provided do not include “complex,” focusing the classification on broad market categories.
• Question seeks common interpretation in basic fertiliser classification.

Concept / Approach:
In everyday trade language and introductory texts, NPK typically denotes a mixed fertiliser, meaning two or more straight fertilisers are blended to a specified analysis. Although some NPKs are complex (chemically combined), within the choices given here, “mixed” is the most appropriate classification differentiating it from single-nutrient products like “potassic.”

Step-by-Step Solution:

Verification / Alternative check:
Fertiliser marketing and extension guides commonly refer to granular blends as “mixed NPKs,” reserving “straights” for single-nutrient products and “complex” for chemically combined multi-nutrient salts.

Why Other Options Are Wrong:

• Potassic: single-nutrient K fertilisers only.
• Liquid or solid: physical state, not classification by nutrient composition.
• Micronutrient-only: NPK concerns macronutrients.

Common Pitfalls:
Assuming all NPKs are complex fertilisers; the question context and options point to the general “mixed” category.

Final Answer:
mixed