Immigration refers to arrival into a country. In the same sense, emigration refers to which action?

Introduction / Context:
Here the relationship is definitional antonymy across paired terms in migration. “Immigration” emphasizes coming in to settle; “emigration” emphasizes going out to settle elsewhere. Therefore the parallel to “arrival” is “leaving” (or “departure”).

Given Data / Assumptions:
We treat “immigration” and “emigration” from the perspective of a reference country.

Concept / Approach:
Maintain the directional contrast. If immigration ↔ arrival, then emigration ↔ leaving/departure. Choices naming people (emigrant, alien) or status (citizenship) do not mirror the action term that matches “arrival”.

Step-by-Step Solution:

Verification / Alternative check:
Migration glossaries list “immigrate = enter” and “emigrate = exit”. Hence “leaving” matches emigration.

Why Other Options Are Wrong:
Emigrant/Alien: persons, not the action; Native: birthplace status; Citizenship: legal status.

Common Pitfalls:
Confusing actor labels with the directional action itself.

Final Answer:
Leaving