When the Law of Diminishing Returns Takes Effect

When the law of diminishing returns takes effect

A) firms must add increasingly more input if they are to maintain the same extra amount of output.
B) firms must add decreasingly more input if they are to maintain the same extra amount of output.
C) more input must be added in order to increase its output.
D) a firm must always try to add the same amount of input to the production process.