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

[EX Q]: Socket secures teeth in the mouth.
[EX A]: What secures teeth in the mouth?

[EX Q]: Potential energy type of energy is possessed by autumn leaves before they fall.
[EX A]: What type of energy is possessed by autumn leaves before they fall?

[EX Q]: Opaque is the term for matter that does not let any light pass through.
[EX A]:
What is the term for matter that does not let any light pass through?