Which of the Following Statements Is True About an Economy

Which of the following statements is true about an economy whose production function includes only capital and labor?

A) Diminishing returns to capital can occur for the economy as a whole.
B) Adding more capital per worker cannot raise real GDP beyond some limit.
C) The production function yields a pessimistic conclusion about economic growth.
D) To get to the point where the return from an additional unit of capital equals zero requires an extremely large investment share of GDP.
E) All of these