If a Single Firm,belonging to a Perfectly Competitive Industry in Long

If a single firm,belonging to a perfectly competitive industry in long run equilibrium,discovers a significant cost saving methodology,then:

A) all firms will enjoy economic profits for a short period of time.
B) the rest of the industry will quickly adopt the new methodology.
C) the firm will enjoy economic profits forever.
D) the firm will lower its price to drive the rest of the industry out of business.