Step 1: Analyze the phrase "Mass departure of people."
The phrase "Mass departure of people" refers to a large-scale movement or exit of people from one place to another.
Step 2: Evaluate the options.
(a) "Exodus" means "a mass departure of people," which directly matches the meaning of the phrase.
(b) "Immigration" refers to the action of coming into a country or region to live, which does not fit the meaning of mass departure.
(c) "Emigration" refers to the act of leaving one`s own country to settle permanently in another, which is similar but not exactly "mass departure."
(d) "Recluse" refers to someone who lives in seclusion, unrelated to the concept of mass departure.
Step 3: Final Answer
The correct answer is (a) Exodus.
Final Answer: The correct answer is (a) Exodus.