In the following question, select the one word substitute that best expresses the meaning of the phrase the return of someone to his own country.

Introduction / Context:
This question focuses on one word substitutes related to movement of people across national borders. The phrase given is the return of someone to his own country. Many English words describe leaving, entering, or returning to countries, and it is easy to confuse them. A clear understanding of these terms is useful in subjects like geography, civics, current affairs, and English vocabulary for exams.

Given Data / Assumptions:

• Phrase to be replaced: the return of someone to his own country.• Options: repatriation, migrate, emigrate, immigrate.• We assume standard dictionary definitions of these terms.• The key idea is return to one's country of origin or citizenship.

Concept / Approach:
Repatriation is the technical term that means sending or returning a person to their own country, especially after war, crisis, employment abroad, or residence in another land. The words migrate, emigrate, and immigrate are related but differ in direction and viewpoint. Migrate is a general term for movement from one place to another. Emigrate means to leave one's own country to live in another. Immigrate means to come into a country to live there. None of these three specifically capture the idea of returning to the home country, which is central here.

Step-by-Step Solution:
Step 1: Focus on the word return, which signals going back to the country of origin.Step 2: Recall that repatriation comes from the Latin roots re meaning back and patria meaning native land or country.Step 3: Check the meaning of migrate, which is a general movement and does not indicate return to the home country.Step 4: Emigrate describes leaving one's own country and settling elsewhere, which is the opposite direction of return.Step 5: Immigrate describes entering another country to live there, again focusing on going to a new place rather than coming back home.Step 6: Since only repatriation clearly means return to the home country, it is the correct one word substitute.

Verification / Alternative check:
Consider an example sentence. After the war, the government arranged for the repatriation of prisoners of war sounds natural and accurate, because it describes organised return to their own country. If we tried After the war, the government arranged for the emigration of prisoners of war, the meaning would be wrong, as it would imply sending them to another foreign country. This confirms that repatriation is the word that correctly matches the idea of return.

Why Other Options Are Wrong:
Migrate is too general and can refer to seasonal movement of birds, temporary movement of workers, or people changing cities within a country. Emigrate always focuses on leaving one's country to settle abroad, not coming back. Immigrate focuses on entering a new country to live there. None of these imply return to the original homeland, so they fail to fully capture the meaning of the phrase in the question.

Common Pitfalls:
Candidates often confuse emigrate and immigrate because they look similar and both involve international movement. A useful trick is to think of emigrate from and immigrate into. Repatriation is different because it is about going back to the patria or fatherland. Remembering these distinctions helps avoid errors in questions that test fine differences in vocabulary related to migration and nationality.

Final Answer:
The correct one word substitute for the return of someone to his own country is Repatriation.