Synonyms are words which have the same or nearly the same meaning in the same language.
Antonyms are words which have opposite meaning in comparison to the other.
Option B)inherent is correct as the word critical means existing in something as a permanent, essential, or characteristic attributeand the word extrinsic means not part of the essential nature of someone or something; coming or operating from outside.
Both the words are opposite of each other.
The other options are not correct as they do not have the opposite meaning to the given word.