The correct option is C. Wind, altitude, humidity, light. Detailed Explanation: To determine which group of factors is completely abiotic, we first need to understand what abiotic factors are. Abiotic factors are the non-living components of an ecosystem that influence living organisms. These include physical and chemical elements such as temperature, water, sunlight, soil, and atmospheric gases. Now, let's analyze each option: Option A: Salinity, tide, plankton, turbidity

• Salinity: This is an abiotic factor that refers to the concentration of salts in water.
• Tide: This is also an abiotic factor, as it relates to the gravitational pull of the moon and sun affecting water levels.
• Plankton: This is a biotic factor. Plankton are small organisms that drift in water and are a crucial part of aquatic food webs.
• Turbidity: This is an abiotic factor that measures how clear water is, often affected by particles suspended in it.

Conclusion: Since plankton is a biotic factor, this option is not completely abiotic. Option B: Temperature, pH, soil, insect

• Temperature: An abiotic factor that affects the metabolic rates of organisms.
• pH: An abiotic factor that measures the acidity or alkalinity of a solution.
• Soil: While soil contains abiotic components (minerals, water), it also contains biotic components (microorganisms, plant roots).
• Insect: This is a biotic factor, as insects are living organisms.

Conclusion: The presence of insects makes this option not completely abiotic. Option C: Wind, altitude, humidity, light

• Wind: An abiotic factor that affects temperature and moisture levels in an environment.
• Altitude: An abiotic factor that refers to the height above sea level, influencing climate and weather patterns.
• Humidity: An abiotic factor that measures the amount of water vapor in the air.
• Light: An abiotic factor that is essential for photosynthesis and affects the behavior and growth of organisms.

Conclusion: All four factors in this option are abiotic, making it the correct choice. Option D: Conifers, wind, pH, rainfall

• Conifers: These are biotic factors, as they are a type of tree that belongs to the plant kingdom.
• Wind: An abiotic factor.
• pH: An abiotic factor.
• Rainfall: An abiotic factor that refers to the precipitation of water.

Conclusion: The presence of conifers makes this option not completely abiotic. Summary of Key Points:

• Abiotic factors are non-living components that affect ecosystems.
• Option C is the only group where all factors (wind, altitude, humidity, light) are abiotic.
• Other options contain biotic factors (like plankton and insects) or mixed factors (like soil with living organisms).
• Understanding the distinction between abiotic and biotic factors is crucial for ecology and environmental science.

Revision Summary:

• Abiotic factors are non-living elements in an ecosystem.
• Option C (Wind, altitude, humidity, light) is entirely abiotic.
• Other options include biotic factors, making them incorrect.
• Recognizing the difference between abiotic and biotic factors is essential for understanding ecological interactions.