Which of the Following Accurately Describes What Is Happening Along

Which of the following accurately describes what is happening along a typical aggregate production function?

A) At some point, increasing the amount of physical capital per worker will reduce productivity.
B) Increases in physical capital per worker will always bring about an increase in productivity that is worth the cost of the additional physical capital.
C) Because of diminishing returns, increasing the amount of physical capital per worker will eventually bring smaller and smaller increases in productivity.
D) Adding workers results in real GDP per worker rising at an increasing rate throughout the function.