If no externalities exist in a particular industry, what happens to the market equilibrium?

Nextdoor is an instant messaging application for smartphones. new smartphone users find it easier to connect with friends and relatives through this mobile app when compared to other similar instant messaging applications. hence, it has the largest user base in the industry. thus, nextdoor app's value has increased primarily due to itsa. learning curve effects. b. economies of scale. c. economies of scope. d. network effects.