Which of the following factors are considered edaphic factors?

Edaphic factors refer specifically to the soil's properties and how they influence the ecosystem. Soil structure encompasses aspects such as texture, composition, porosity, and the arrangement of soil particles, which directly affect water retention, root penetration, and the availability of nutrients to plants. These soil characteristics play a crucial role in determining the types of vegetation that can thrive in a particular area and, consequently, influence the entire ecosystem.

The other options pertain to different types of environmental factors. Climate involves atmospheric conditions such as temperature, rainfall, and humidity, which are not directly related to the soil itself. Topography refers to the physical terrain and landscape features, which can influence drainage and sunlight but again do not constitute soil characteristics. Finally, biotic interactions involve the relationships between living organisms, such as competition and predation, rather than being related to soil properties. Therefore, the factor that truly defines edaphic influences is soil structure.