Suppose that each worker must use only one shovel to dig a trench, and shovels are useless by themselves. In the long run, an increase in the price of shovels will result in
A) fewer shovels being purchased to produce the same number of trenches.
B) more workers being hired to produce the same number of trenches.
C) the firm wishing to produce more trenches.
D) no change in the firm's input mix.
Answer: no change in the firm's input mix.