The answer is (d.) mov(e). A free morpheme means a word that can stand alone. In the word REMOVAL, the word move can leave out and can stand on its own since it has its own meaning. The word move doesn't need prefixes to have a meaning.
I would say because people separated from their kind and leading to speaking different. just like how people pick up accents when they go to the UK or other foreign countries.
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The word incontrovertible is positive.
