(A) ** A narrow strip of land that connects two larger areas.
(B) A trade route
(C) A hole in the ground used for war
(D) A path submarines took to travel
EXPLANATIONS BELOW
Concept note-1: -An isthmus is a narrow strip of land that connects two larger landmasses and separates two bodies of water. This type of isthmus is called a tombolo, and is formed as waves and tides slowly build up a sand bar to create a permanent link between a coastal island (called a tied island) and the mainland.