There Are Externalities Associated with Entry into a Monopolistically Competitive

There are externalities associated with entry into a monopolistically competitive market.The product-variety externality arises because:

A) new firms offer products different to the existing firms, and consumers value choice
B) incumbent firms offer a range of differentiated products, which is valued by consumers
C) entry increases competition and lowers prices, which benefits all consumers
D) firms post a price above marginal cost and are eager to sell too many units