Correct Answer: Hematology : Blood

Solution : Given:
Phycology : Algae (Here, Phycology is the scientific study of algae.)

First option: Eccrinology : Amphibians; Eccrinology is the branch of medical science concerned with secretions of the eccrine glands.
Second option: Selenography : Secretions; Selenography is the study of the moon's surface.
Third option: Hematology : Blood; Hematology is the study of blood and blood disorders.
Fourth option: Entomology : Soil; Entomology is the scientific study of insects.

So, only the third option follows the same pattern as followed by the given pair of words. Hence, the third option is correct.