According to the lump of labor fallacy, if the economy were a pie, which of the following would be correct?

a$.$ The size of the pie is shrinking, so the pieces are getting smaller over time.

b$.$ The size of the pie is not important; the quality of the pie is what matters.

c$.$ The size of the pie is fixed, so for one piece to get larger, other pieces must get smaller.

d$.$ The size of the pie is growing, so the pieces are getting bigger over time.