Final answer:
Point B represents a recessionary phase with rising unemployment and falling GDP, while Point D represents an expansionary phase with falling unemployment and rising GDP.
Step-by-step explanation:
The key difference between Point B and Point D on a business cycle graph lies in the economic indicators associated with each phase. Point B, marked by a black arrow spanning the fall between Point A and Point C, represents a period of economic decline where indicators such as Gross Domestic Product (GDP) and employment typically fall — signaling a phase of contraction or recession. Conversely, Point D, with a black arrow spanning the rise between Point C and Point E, indicates a period of economic growth where GDP rises, and unemployment typically decreases, reflecting an expansion phase or a boom.
Therefore, the correct description of a key difference between B and D would be that unemployment rises in B but falls in D, representative of a movement from peak to trough (B) and trough to peak (D) within the business cycle.