Explanation:
The Earth is comprised of many plates that float on the hot magma in the mantle layer. They are constantly moving but its so slow we can't feel it. A long time ago, all the land on Earth was connected in one big continent named Pangaea. As the plates have moved the land has separated forming the continents.
When plates come together they cause friction between them. This causes the plates to push up forming a mountain. This was how the Himalayan mountains were formed.
So to clarify is the geographer "human" or is it geographing humans
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