If the Price of an Input Falls,a Firm Would Increase

Multiple Choice

If the price of an input falls,a firm would increase the use of that input for two reasons:

A) the input is now more productive,and the firm can substitute this input for other relatively more expensive inputs.
B) the input is now more productive,and overall production costs are now lower,meaning a firm may choose to increase production.
C) overall production costs are now lower and the firm can substitute this input for other relatively more expensive inputs.
D) overall production costs are now lower and the firm will have more of other inputs to use with the one in question.