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

Chordates include vertebrates and invertebrates that have a notochord.
Chordates include vertebrates and invertebrates that have what?

A skeleton that consists of hard, mineralized structures located within the soft tissue of organisms is called endoskeleton.
A skeleton that consists of hard, mineralized structures located within the soft tissue of organisms is called what?

Two many atoms of oxygen does silicon dioxide contain.
How many atoms of oxygen does silicon dioxide contain?