The Groins are hard structures and used to maintain uplift beaches as to restrict longshore sediment transportation form tasking place. Are meant to capture sand transportation by the currents.
While the jetty is another type of shore perpendicular structure that is placed adjacent to the tidal inlets and controls the inlet migration. Both of them are used to destabilize coastal systems and disrupt the natural sediment regimes.
The corecct anwser would be C mongolia. This is known as the 3rd most least densely populated countries in the world. with Greenland in 1st and Falkland Islands as 2nd.
