Edaphology is
a. Study of snakes
b. Study of amphibians
c. Study of elephants
d. Study of soils

Hint: There are different studies in the field of biology, where the name of every study has two parts, that are prefix and the suffix, and the prefix name varies in every study and it mainly depends on the type of study, where has logy is a suffix, that represents the branch or field.

Complete answer:
- It is the Greek word, where the edaphos means ground and logy means to study, this edaphology is mainly concerned with the study of soil which is in relation to biological things.
- It is mainly concerned with the soil science of plants, where this soil science has two divisions, that is one edaphology and the other one is pedology.
- Again this edaphology has two subdivisions, which are Agriculture soil science and environmental soil science.

Agriculture soil science
- It is mainly concerned with the application of soil chemistry, physics, biology with the relation of crops.
- When coming to soil chemistry, it mainly deals with soil nutrition and mainly regarding the fertility of the soil.
- Physics in agriculture edaphology mainly deals with irrigation and drainage.

Environmental soil science
- It mainly deals with our interactions with the pedosphere in the field of crop production.
- It also deals with soil erosion and land treatment with wastewater and rainwater, and it also deals with soil contamination, septic drain field, and also environmental nutrients, etc.

Hence, the correct answer is option (D).

Note: Study of soil has mainly 2 types of studies where they are pedology, they mainly deal with soil science and soil orders found in India, whereas edaphology is mainly with the soil concerned with plant biology.