A great deal of means a large amount or quantity of something. The correct answer is this meaning because the expression is used figuratively, not only by its literal words.

Examples:

• The project required a great deal of patience and research.
• In an HSC essay, A great deal of can express this meaning: a large amount or quantity of something.
• When this expression appears in a passage, connect A great deal of with the idea of a large amount or quantity of something.