Thermosphere is the answer
The correct answer is - D. It is impossible to dig through the ice on Antarctica.
Even though the technology is much more advanced nowadays than in the past, the extraction of the numerous natural resources from Antarctica is still pretty much impossible because of the ice cover over the continent.
On average, the ice is around 2 km thick on top of the landmass. Considering the fact that in order to get to the resources, the people will have to dig even more into the ground after they manage to break through the ice, makes it almost impossible, and not to mention economically unjustifiable.
Every river and it's flow has source and mouth: source is the part of the flow of the river- the place where the river starts and mouth is the part where the river flows into a sea or lake.
Answer:
Vatican City is the smallest country in the world
