Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

Poles parts of the planet does solar energy have difficulty reaching.
What parts of the planet does solar energy have difficulty reaching?

Toxins is contained in the skin of brightly colored poison dart frogs.
What is contained in the skin of brightly colored poison dart frogs?

Woolly mammoths began to go extinct thousands of years ago because of hunting by humans.

Why did woolly mammoths began to go extinct thousands of years ago?