The correct answer is narrowing.
A. small island
The correct answer is (C) A narrowing (of land connecting two larger pieces); a narrow strip of land, bordered on both sides by water, which joins two larger areas.
Isthmus comes from Greek isthmos (neck).
Examples of use:
- The excavation for the canal cut across the Isthmus of Panama.
- The road along the isthmus is subjected to spray during windy periods.