An article of faith means a strong belief accepted without question. The correct answer is this meaning because the expression is used figuratively, not only by its literal words.

Examples:

• For the reformer, free speech was an article of faith.
• In an HSC essay, An article of faith can express this meaning: a strong belief accepted without question.
• When this expression appears in a passage, connect An article of faith with the idea of a strong belief accepted without question.