Autochthonous means indigenous rather than descended from migrants or colonists.
Hence option C is clearly the correct answer because “indigenous “ means originating from a particular place hence it is correct.
Option A is incorrect because “original” is the property of not being false or fake, hence it is not the correct meaning of the given word.
Option B is incorrect because “majority “ means the greater number, hence it is not relevant to the given word.
Option D is incorrect because “important “ means something that is significant, hence it is not related to the given word.