Which statement describes the short run in production?

• A. All inputs fixed
• B. Capital fixed while some inputs vary
• C. All inputs variable
• D. No production possible

Answer: (B)

In the short run, a firm can’t adjust all of its inputs at once; some inputs are fixed. Typically, the capital stock—things like the plant, machines, and facilities—remains unchanged in the short run, while variable inputs such as labor and raw materials can be adjusted to change output. That means production decisions hinge on how efficiently you use the existing plant with the varying inputs you can control. By contrast, in the long run all inputs are variable, so the firm can alter capital as well as labor and materials. Saying all inputs are fixed would imply no production flexibility at all, which isn’t how the short run is defined, and saying all inputs are variable describes the long run.