Answer: Option D
Explanation: Network externalities are indeed an economic principle that defines the conditions in which a product or service's value increases or decreases as the number of customers increases or declines.
As the availability of an item raises the price of the product falls it becomes less valuable, according to the traditional economic theory. This is termed "positive externalities of the network" or "network influence."
Thus, somehow it creates barriers for other firms by prepairng a strong customer base for an experienced firm.