Which of the following is concerned with soil?

1. A

   Edaphic

   Edaphic factors are those that arise from the soil itself: texture, structure, pH, moisture, organic matter and mineral nutrients. Plant and animal communities on a site are shaped by these soil properties as much as by climate. The word is the standard ecological term for the soil complex. This option is therefore the official key.

2. B

   Climatic

   Climatic factors are temperature, rainfall, humidity, wind and light. They act through the atmosphere, not through the soil profile. Climate is a separate ecological factor from the edaphic set. This option is not the key.

3. C

   Biotic

   Biotic factors are the living components: plants, animals, microbes and their interactions such as competition and predation. They are not a name for soil. This option is therefore wrong.

4. D

   Topography

   Topography means the lie of the land: slope, aspect and elevation. Relief modifies climate and drainage, but it is not itself the soil factor. This option is not the key.

Summary. Official key is (a) Edaphic. In ecology the environment is split into climatic, edaphic, topographic and biotic factors. Edaphic specifically means soil-borne properties that govern vegetation. Climate, living organisms and relief are other headings, not synonyms of soil. Only (a) is concerned with soil as asked.