The correct option is D entry
The word 'exodus' refers to a mass departure of people.
Option A, expulsion refers to the action of forcing someone to leave a place.
Option B, invasion refers to an instance of invading in a country using an armed force.
Option C, immigration refers to the action of coming to live permanently in a foreign country.
Option D, entry refers to an act of going or coming in.
Thus, according to the meaning, the word 'entry' is the opposite of the word 'exodus'.