The correct way to make the word "visible" into an adverb is "visibly". So the correct option among all the options given in the question is option "A". To answer these type of questions, it is important to understand the meaning of adverb first. An adverb is actually a word that modifies a verb, adjective, another adverb, noun phrase sentence and clause. Adverbs are considered traditionally as parts of speech. There are numerous sentences used by us where the word visibly is used.