Inherent is a word that comes from the Latin "inhaerens" and it is a conjugation of the verb "inhaerere" ("remain united"). The concept is used to name that which, due to its natural conditions, it is impossible to separate it from something since it is united in an indivisible way to that. Synonyms of the word include: essential, intrinsic, built-in, fundamental, innate. The answer is A. "Essential".