A root word has no prefix or suffix and is the most basic part of a word. The prefix of the word 'unreasonable' is 'un'. The root word is 'reasonable.'
I believe the correct answer is the third one.
Neither. Dormant and recessive are not synonyms because their definitions are not similar, nor are they antonyms because they aren't opposites, either. Dormant means to sleep. Recessive refers to a trait that is usually masked by a dominant trait.
Hope that answered your question.