Choose the word which is different from the rest.

The answer is D. Oasis.

An island is a piece of land surrounded by water on all sides. A coast is the land along the edge of an ocean or sea. A harbour is a sheltered area of water where ships can dock. A peninsula is a piece of land that is surrounded by water on three sides. An oasis is a small area of vegetation in a desert.

Oasis is the only option that is not a landform. The other options are all landforms.