Land so surrounded by water as to be almost an island

Answer: Option C

One word substitute is Peninsula.

Archipelago: an extensive group of islands.
Isthmus: a narrow strip of land with sea on either side, forming a link between two larger areas of land.
Peninsula: a piece of land almost surrounded by water or projecting out into a body of water.
Lagoon: a stretch of salt water separated from the sea by a low sandbank or coral reef.