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

Example Input: When magma heats groundwater, it may come to the surface as a hot spring or a geyser.
Example Output: When magma heats groundwater, it may come to the surface as a hot spring or a what?

Example Input: Some compounds form rigid frameworks called crystals.
Example Output: Some compounds form rigid frameworks called what?

Example Input: Monatomic ions form when a single atom gains or loses electrons.
Example Output:
What form when a single atom gains or loses electrons?