In the following question, out of the four alternatives, choose the one which can be substituted for the given words/sentence. The systematic study of cultures, especially the comparison and analysis of different human societies and their customs.

Introduction / Context:
This question belongs to the category of one word substitutes that deal with academic disciplines. The phrase "study of cultures" points to a specific branch of anthropology that focuses on different human groups, their customs, beliefs, and social structures. Knowing the correct term helps in understanding social sciences, reading academic texts, and solving exam questions accurately.

Given Data / Assumptions:

• We are dealing with the study of cultures, not language origins, animal behaviour, or physical geography.
• The options are eremology, etymology, ethology, ethnology, and sociology.
• The correct answer must refer directly to the scientific study of cultures and societies.

Concept / Approach:
"Ethnology" is the branch of anthropology that compares and analyses cultures, especially with respect to their origins, distribution, technology, religion, language, and social structure. It is different from "ethology," which studies animal behaviour, and "etymology," which studies the origin and history of words. While "sociology" also studies society, the more precise term for the comparative study of cultures is ethnology, and that is what examinations typically test in such questions.

Step-by-Step Solution:
Step 1: Identify the core idea: systematic study of cultures and societies.Step 2: Examine "eremology," which refers to the study of deserts and lonely places, not cultures.Step 3: Examine "etymology," which refers to the study of the origin and history of words.Step 4: Examine "ethology," which is the scientific study of animal behaviour, especially under natural conditions.Step 5: Examine "ethnology," a field in anthropology that compares different cultures and analyses their development.Step 6: Recognise that "sociology" studies human society in a broader sense, including institutions and social relationships, but the exact exam oriented term for "study of cultures" given here is ethnology.

Verification / Alternative check:
Imagine a researcher who travels to various tribal communities, observes rituals, collects data on marriage customs, belief systems, and social hierarchy, and then compares these across different groups. This researcher is working in ethnology. If the same researcher studied how words for family members have changed over centuries, that would be etymology instead. If they observed how animals behave in groups, that would be ethology. This mental distinction confirms that ethnology is the best match for the description in the question.

Why Other Options Are Wrong:
"Eremology" is about deserts and desolate regions, unrelated to culture. "Etymology" deals with the origin of words, not the customs of human societies. "Ethology" studies animal behaviour rather than human cultural patterns. "Sociology" is close but broader and not as precise as ethnology for this question, which explicitly highlights the idea of cultures rather than society in general.

Common Pitfalls:
Many students confuse ethnology with ethology because the words look similar and both begin with "etho." Remember that "ethnos" in Greek refers to people or nation, leading to ethnology, the study of peoples and cultures. "Etymon" relates to true meaning of a word, which gives etymology. Distinguishing these root meanings helps you remember and correctly answer word substitute questions in exams.

Final Answer:
ethnology