Consider a Perfectly Competitive Industry in a Long-Run Equilibrium

Consider a perfectly competitive industry in a long-run equilibrium. If a single firm in that industry discovers a significant cost-saving production technology, then:

A) all firms in the market will earn an economic profit in the short run.
B) the rest of the industry will quickly adopt the new technology.
C) the firm will earn an economic profit in the long run.
D) all the firms in the market will earn an economic profit in the long run.