Which of the following statements illustrates diminishing returns​? A. The second billion hours of labor changes real GDP from​ $1 to​ $3 trillion and the third billion hours of labor changes real GDP from​ $3 to​ $4 trillion. B. The second billion hours of labor changes real GDP from​ $1 to​ $2 trillion and the third billion hours of labor changes real GDP from​ $2 to​ $3 trillion. C. The second billion hours of labor changes real GDP from​ $1 to​ $2 trillion and the third billion hours of labor changes real GDP from​ $2 to​ $4 trillion. D. The second billion hours of labor changes real GDP from​ $1 to​ $5 trillion and the third billion hours of labor changes real GDP from​ $5 to​ $9 trillion.