Costs Are Clearly Minimized for a Given Level of Output

Multiple Choice

Costs are clearly minimized for a given level of output as long as the firm

A) uses inputs that do not exhibit declining productivity.
B) pays the same price for all of its inputs.
C) is not able to increase output by substituting a dollar's worth of input A for a dollar's worth of input B, or vice versa.
D) can increase output without increasing its cost.
E) equates the marginal products of both inputs A and B.