A rough-and-ready method means a simple practical method that is not exact or polished. The correct answer is this meaning because the expression is used figuratively, not only by its literal words.

Examples:

• We used a rough-and-ready method to estimate the crowd.
• In an HSC essay, A rough-and-ready method can express this meaning: a simple practical method that is not exact or polished.
• When this expression appears in a passage, connect A rough-and-ready method with the idea of a simple practical method that is not exact or polished.