What is a production function? How does a long-run production function differ from a short-run production function? A. A function showing the minimum output that a firm can produce for every specified combination of inputs. In the short-run production function, all inputs are variable, whereas the long-run production function has at least one fixed input.. B. A function showing the highest output that a firm can produce for every specified combination of inputs. In the short-run production function, all inputs are variable, whereas the long-run production function has at least one fixed input. C. A function showing the minimum output that a firm can produce for every specified combination of inputs. In the long-run production function, all inputs are variable, whereas the short-run production function has at least one fixed input. D. A function showing the highest output that a firm can produce for every specified combination of inputs. In the long-run production function, all inputs are variable, whereas the short-run production function has at least one fixed input.