To accurately determine which point(s) represent efficient production in Figure 2-3, I would need to see the figure itself or have a description of it. However, in general terms, efficient production in a production possibilities frontier (PPF) context typically occurs on the curve itself (not inside or outside it).
If you can provide more context or describe the points A, B, C, and D, I’d be happy to help you identify the correct answer based on that information!