What are the principal conditions that allow monopolies to exist?

A. Licenses

B. Barriers to entry

C. Technologies

D. Price discrimination

B: Barriers to entry.

Barriers to entry prevent other firms from joining the market.

Answer: B: Barriers to entry

Barriers to entry are the principal conditions that allow monopolies to exist.

Explanation:

A monopoly refers to an industry or a market where there is a single seller selling a special or unique product. The seller is the sole seller of a product with no close substitute and as such the seller does not face competition. The monopolist decides the price in the market and maintains super normal profit in the long.