Given a scientific question, generate a correct answer to it.

Input: Consider Input: Which theory describes the benzene molecule and other planar aromatic hydrocarbon molecules as hexagonal rings of sp2-hybridized carbon atoms with the unhybridized p orbital of each carbon atom perpendicular to the plane of the ring?

Output: valence bond theory

Input: Consider Input: What is the term for a symbiotic relationship in which one species benefits while the other species is not affected?

Output: commensalism

Input: Consider Input: What is it called when crystals form from magma?
Output: crystallization