参考答案：B

解析：

The short run is defined at the period during which the quantities of other inputs are fixed. In the long run a firm’s demand for capital is more elastic because technology, the amount of labor, and the quantities of other inputs can be varied. A firm’s demand for labor is more elastic in the long run than in the short run. For a given increase in wage rates, a firm’s quantity of labor demand will decrease more when it can substitute other factors of production (the long run) than when other factors are fixed (the short run).