Good Z Is Produced and Sold in a Competitive Industry,and

Good Z is produced and sold in a competitive industry,and long-run industry supply is characterized by constant costs.The figure below shows a typical long-run average cost curve (LAC) for each of the firms producing good Z.LAC reaches its minimum unit cost of $12 and 1,000 units of output (point M) . The long-run industry supply curve for this constant cost industry will be a

A) vertical line at 1,000 units because supply is perfectly inelastic in this case.
B) vertical line at $12 because supply is perfectly inelastic in this case.
C) vertical line at 0 because supply is perfectly inelastic in this case.
D) horizontal line at $0 because supply is perfectly elastic in this case.
E) horizontal line at $12 because supply is perfectly elastic in this case.