instruction:
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
question:
The seven unique crystal types are defined by faces parts of themselves (parts that intersect at various angles).
answer:
The seven unique crystal types are defined by what parts of themselves (parts that intersect at various angles)?


question:
The sound in a loud classroom is an example of a form of energy.
answer:
Which of the following is an example of a form of energy?


question:
We call the solid form of hydrocarbons coal.
answer:
What do we call the solid form of hydrocarbons?