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

[Q]: Learning to get used to something after being exposed to it for a while is associated with what kind of learning?
[A]: habituation

[Q]: What is the term for a symbiotic relationship in which one species benefits while the other species is not affected?
[A]: commensalism

[Q]: Matter can exist either as a pure substance or as a combination of what?
[A]:
different substances