A leap in the dark means a risky action taken without knowing the result. The correct answer is this meaning because the expression is used figuratively, not only by its literal words.

Examples:

• Starting the business without research was a leap in the dark.
• In an HSC essay, A leap in the dark can express this meaning: a risky action taken without knowing the result.
• When this expression appears in a passage, connect A leap in the dark with the idea of a risky action taken without knowing the result.