Which of the Following Physical Relationships Might Generate Economies of Scale

Multiple Choice

Which of the following physical relationships might generate economies of scale?

A) Proportionally larger pipes can transport more than a proportional increase in oil.
B) Larger equipment tends to weigh more and use more fuel on a per-unit-of-output basis.
C) Each lift truck requires one lift truck driver.
D) A doubling of all inputs leads to a doubling of output.