A race against time means an urgent effort to finish something before a deadline. The correct answer is this meaning because the expression is used figuratively, not only by its literal words.

Examples:

• Rescuers were in a race against time after the storm.
• In an HSC essay, A race against time can express this meaning: an urgent effort to finish something before a deadline.
• When this expression appears in a passage, connect A race against time with the idea of an urgent effort to finish something before a deadline.