Marginal returns refer to the additional output resulting from a one unit increase in the use of variable inputs, while other inputs are held constant.

• A. The total output from all inputs
• B. The rate of return on investment
• C. The cost of additional inputs
• D. The additional output from a one unit increase in the use of variable inputs, while other inputs are held constant

Answer: (D)

Marginal returns measure the extra output produced by adding one more unit of a variable input, while keeping all other inputs fixed. This focuses on the change in output from a single incremental input, which is what “marginal” is about in production analysis. The idea is different from total output, which sums all production, and from rate of return on investment or cost, which relate to profitability and expense rather than the incremental change in output. In practice, as you add more of a variable input with a fixed amount of other inputs, the additional output you gain from each new unit often rises at first and then falls, illustrating diminishing marginal returns. The statement exactly captures this incremental-output concept.