(A) ** blockade
(B) guerrilla warfare
(C) mercenary
(D) duty
EXPLANATIONS BELOW
Concept note-1: -Terms and People blockade – the shutting off of a port by ships to keep people or supplies from moving in or out mercenary – soldier who serves another.
Concept note-2: -blockade, an act of war whereby one party blocks entry to or departure from a defined part of an enemy’s territory, most often its coasts.
Concept note-3: -A blockade is the act of actively preventing a country or region from receiving or sending out food, supplies, weapons, or communications, and sometimes people, by military force.