A turning point means a decisive moment when an important change begins. The correct answer is this meaning because the expression is used figuratively, not only by its literal words.

Examples:

• The scholarship was a turning point in her life.
• In an HSC essay, A turning point can express this meaning: a decisive moment when an important change begins.
• When this expression appears in a passage, connect A turning point with the idea of a decisive moment when an important change begins.