Which of the following statements are correct regarding the Producer Theory?

A) The production function represents the relationship between input quantities and output quantities produced.
B) The law of diminishing returns states that as more units of a variable factor are added to fixed factors, the additional output eventually decreases.
C) The short-run supply curve is derived from the marginal cost curve above the average variable cost curve.
D) In the long run, the producer cannot adjust the input quantities to minimize costs.