On the medieval world-maps it was represented only the part of the world known as the 'old world', which is consisted of Europe, Asia and Africa. Before the big discoveries, people living in this continents had knowledge only of this part of the world, while South and North America, Australia and Antarctica where still unknown to them, thus they are missing in the world-maps of this period.
The greenhouse effect is the rise in temperature that the Earth experiences because certain gases in the atmosphere (water vapor, carbon dioxide, nitrous oxide, and methane, for example) trap energy from the sun. Normal warming is mostly caused by natural gases.
The answer to your question is d :)
The answer is the urals and the caucasus mountains
