Which of the following is a man-made structure meant to protect a waterway from wave action and longshore drift? Groin Sand bar Jetty Wharf

The man-made structure meant to protect a waterway from wave action and longshore drift is a Jetty.

Here's a step-by-step explanation:

1. A Groin is a man-made structure designed to trap sand as it is moved down the beach by the longshore drift. As the longshore drift is interrupted, sand will be deposited on the updrift side (the side the waves are coming from), but eroded from the downdrift side.

2. A Sand bar is a natural landform that develops in certain conditions along the shoreline. It is not man-made.

3. A Jetty is a man-made structure that projects from the land out into water. Often, "jetty" refers to a walkway accessing the centre of an enclosed waterbody. The term derives from the French word jetée, "thrown", signifying something thrown out. Jetties may protect the coastline from the effects of weather and longshore drift.

4. A Wharf is a structure on the shore of a harbor or on the bank of a river or canal where ships may dock to load and unload cargo or passengers. It doesn't protect a waterway from wave action and longshore drift.

So, the correct answer is Jetty.