Answer:
Reinforcement is the process by which natural selection increases reproductive isolation. Reinforcement can occur as follows: When two populations which have been kept apart, come back into contact, the reproductive isolation between them might be complete or incomplete. If it is complete, speciation has occurred.
Explanation:
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Liquids are measured by liters.
solids are measured by cubic units.
I think it will change, because over the years they have found different ways to show the atom, and different discoveries. We always have a new chance to discover something new about the atom.