If C(x) gives the cost in dollars of producing x items of a certain product, which of the following statements are true about dC/dx , the derivative of C(x) ?
I. The units of dC/dx are dollars per item.
II. The value of dC/dx at any value of x is the change in cost per item produced.
III. dC/dx is the rate at which items are produced.
(A) I only
(B) II only
(C) I and II only
(D) I, II, and III
