(A) Dreadnoughts
(B) ** U-Boats
(C) Airplanes
EXPLANATIONS BELOW
Concept note-1: -Aircraft radar also evolved to became one the best ways to hunt submarines. Towards the end of WWII radar equipped aircraft is credited for most of Allied kills against U-Boats.
Concept note-2: -Of the 373 German submarines that had been built, 178 were lost by enemy action. Of these, 40 were sunk by mines, 30 by depth charges, and 13 by Q-ships; 512 officers and 4894 enlisted men were killed.
Concept note-3: -ASDIC / Sonar This was the main detection device used on a submerged U-boat in World War Two and has been dramatized in numerous movies through its distintive “ping” sound.
Concept note-4: -The use of ASDIC (SONAR) became widespread and so did the installation of shipboard and airborne radar. The Allies Ultra code breaking allowed convoys to be steered around German U-Boat wolfpacks.