Answer:
A. consumer surplus that is generated from the introduction of a new product.
Explanation:
The product-variety externality is defined as consumer get the surplus that is generated from the introduction of a new product and entry of a new firm conveys a positive externality on consumers. It arises as new firms offer products that differ from those of the existing firms, however, it does not happen under perfect competition. Competitive market lead to efficient outcomes, unless there are externalities.
