Go out of fashion means to become no longer popular or common. The correct answer is this meaning because the expression is used figuratively, not only by its literal words.

Examples:

• Some old expressions go out of fashion.
• In an HSC essay, Go out of fashion can express this meaning: to become no longer popular or common.
• When this expression appears in a passage, connect Go out of fashion with the idea of to become no longer popular or common.