The Demand Curve Facing a Firm Acts as a Constraint

The demand curve facing a firm acts as a constraint by

A) shifting to the left and right as suppliers vary their quantities
B) showing the maximum price that could be charged to sell a specific output level
C) showing the minimum quantity of output that a firm needs to produce at a specific price
D) limiting sales to those who are first in line when the product is distributed
E) relating the actions and decisions of buyers and sellers in the market