Question

7 what makes the top layers of soil darker in color than the lower layers?
○ a small amount of organic matter
○ very young soil
○ iron oxide
○ a large amount of organic matter

Explanation:

The top soil layers (topsoil) accumulate decaying plant and animal material, which is organic matter. This abundant organic matter gives the upper soil a darker brown or black color, while lower subsoil layers have far less organic content and are lighter. The other options are incorrect: small organic matter would not darken the soil, young soil lacks accumulated organic material, and iron oxide typically creates reddish or yellowish soil tones, not dark top layers.

Answer:

D. a large amount of organic matter