Which Statement Defines Business-Stealing Externality

Which statement defines business-stealing externality

A) It is the positive externality associated with the gains of consumer surplus in a monopolistically competitive market.
B) It occurs when one firm attempts to exactly duplicate exactly the product of another firm.
C) It is considered to be an explicit cost of business in monopolistically competitive markets.
D) It is the negative externality associated with entry of new firms in a monopolistically competitive market.