Lagos ,Nigeria kinda cool
This statement is false. There is actually five types of plains. The five types of plains are coastal plain, alluvial plain, glacial plain, terrestrial plain and flood plain. Plains are flat areas that are usually located in lowlands and at the bottom of the valleys.
The Rocky Mountains are described as younger because the Rocky's are really two mountain chains. The older mountain chain started billions of years ago, and the younger mountain chain pushed the older mountain chain up more, only 60 millions years ago.
Cambodia and Vietnam are not island nations: they are not placed on islands, but on the Indochina Peninsula in Asia - so they can't be the correct answer
Indonesia is an island nation, but it's a presidential republic, not a monarchy.
The correct answer is Brunei