Which of the following factors is critical in determining how effectively a solid fuel burns?

The effectiveness of solid fuel combustion is predominantly influenced by configuration. Configuration refers to how the solid fuel is arranged and shaped for combustion. This can include aspects such as the size and shape of the fuel particles, how densely they are packed, and the spacing between them. An optimal configuration promotes better airflow, which is crucial for combustion. Proper airflow allows for more efficient burning by providing the necessary oxygen for the fuel to ignite and sustain fire.

In contrast, while moisture content is important as it can impede the burning process by requiring energy to evaporate water before combustion can occur, the arrangement of the fuel itself has a more direct impact on the combustion dynamics. Color and price are generally unrelated to combustion efficiency; color does not affect how well a solid fuel burns, and price is a factor of economic consideration rather than combustion characteristics.