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

Input: Consider Input: Matter that mechanical wave energy can only travel through is medium.

Output: What is the name of matter that mechanical wave energy can only travel through?


Input: Consider Input: The ability of matter to combine chemically with other substances is known as reactivity.

Output: The ability of matter to combine chemically with other substances is known as?


Input: Consider Input: Solid type of hydrocarbon is coal.
Output: What type of hydrocarbon is coal?