One Requirement for an Industry to Be Perfectly Competitive Is

One requirement for an industry to be perfectly competitive is that in the industry there

A) are a few firms who control the market.
B) are many firms for whom the efficient scale of production is small.
C) is one firm that sells a product with no close substitutes.
D) are many firms selling different products.
E) is a barrier to entry that makes the entry of new firms difficult.