Consider the Short-Run Supply Curve for a Perfectly Competitive Industry

Multiple Choice

Consider the short-run supply curve for a perfectly competitive industry.In general,which of the following statements are true?

A) The short-run industry supply is obtained by horizontally summing the supply curves of all the individual firms in the industry.
B) The industry supply curve tends to be flatter more elastic) than the horizontal sum of all the industrial firms' supply curves.
C) Short-run supply for a perfectly competitive industry is flat for constant cost industries.
D) both a and b
E) none of the above are true in general