Concept:The correct word must be the opposite of the underlined word and also fit the sentence naturally.Explanation:The underlined word is "obscure"."Obscure" means something not clearly expressed or not easy to understand.The opposite of "obscure" is "obvious"."Obvious" means easily seen, understood, or recognised.It fits the gap because it gives the required opposite meaning.The other options do not provide the correct opposite meaning.Answer:B. obvious