The Short-Run Industry Supply Curve

The short-run industry supply curve:

A) shows the total quantity supplied by all firms in an industry for each possible price when the number of producers is fixed.
B) is drawn on the assumption that the number of firms in the industry doesn't increase,but it allows for a decrease in the number of firms due to bankrupt firms leaving the industry.
C) is a meaningful concept only if all firms in the industry are identical.
D) is of limited usefulness since it is not relevant when markets are perfectly competitive.