Answer: melting glaciers
The question is:
The fjords of Norway have been formed by____.
O Melting glaciers
O The North Atlantic Current
O Volcanic action
O Global warming of previous eras
O Pollution from seaside factory output
The question is asking, "what were the fjords of Norway formed by?"
What is a "Fjord"?
A fjord is a deep, high-walled coastal valley created by glacier movement and filled by the waters of melting glaciers.
What is a "Glacier"?
Glaciers are a slow-moving river of snow and ice that moves on the earth's surface.
Why is "melting glaciers" the correct answer?
Well, the truth is, the earth is heating up. Humans use a lot of fossil fuels (non-renewable energy), and the waste that comes from our common engines and motors is known as CO₂ or carbon dioxide (the prefix "di" in "dioxide" means two, so if we want to say that there are two oxide particles, then we would say "dioxide.") CO₂ can cause the atmospheres to become denser and trap more of the sun's heat, like the greenhouse effect. This dramatic change in temperature has caused glaciers to melt but also move, making the sea levels higher and/or creating fjords.