(A) Blockade
(B) Trench Warfare
(C) ** Convoy
EXPLANATIONS BELOW
Concept note-1: -A K-ship helped escort the submarine into port, marking the end of anti-submarine warfare duties for K-ships in the battle of the Atlantic. K-ships provided critical protection to convoys carrying the vital supplies needed to win World War II. In his work, Blimps and U-Boats, J.
Concept note-2: -The convoy system consists of a group of merchant ships sailing together under the protection of larger and/or more heavily armed ships. The system was created to help better protect cargo and passengers on ships that were sailing through treacherous waters.
Concept note-3: -The convoy system, or a group of merchant ships sailing together for protection, has a long naval history. It was used extensively by Spain to protect its treasure fleets against pirates in the colonial period.
Concept note-4: -One U-boat would shadow a convoy and summon others by radio, and then the group would attack, generally on the surface at night. These tactics succeeded until radar came to the aid of the escorts and until convoys could be given continuous sea and air escort all the way across the Atlantic in both directions.