Come into one's own means to reach a stage where one's ability or value is fully shown. The correct answer is this meaning because the expression is used figuratively, not only by its literal words.

Examples:

• The young singer came into her own during the concert.
• In an HSC essay, Come into one's own can express this meaning: to reach a stage where one's ability or value is fully shown.
• When this expression appears in a passage, connect Come into one's own with the idea of to reach a stage where one's ability or value is fully shown.